[AntibioticScout.ch: Decision support for the prudent use of antimicrobials: Application in cattle]. / AntibioticScout.ch: Entscheidungshilfe für den umsichtigen Einsatz von antimikrobiellen Wirkstoffen: Anwendung beim Rind.

INTRODUCTION: The administration of antibiotics in livestock has been criticized for many years, in particular because of an inappropriate use and the appearance of antibiotic residues in the environment, which can promote the emergence and spread of resistant bacteria. However, antibiotics are essential for the successful and sustainable control of bacterial pathogens. With the aim of optimizing the use of antibiotics in food animals and minimizing the prevalence of resistant bacteria, AntibioticScout. ch provides a decision aid for the prudent use of antimicrobial drugs. This approach emphasizes the importance of supportive therapy and the hallmarks of preventive concepts. Procedures to improve animal health and animal welfare in accordance with the principles of good veterinary practice are primary and effective tools to reduce the use of antimicrobial drugs. The necessary reduction in the use of antibiotics must, therefore, be accompanied by appropriate management strategies in animal husbandry. In particular, hygiene, animal welfare and biosecurity measures are crucial to ensure an optimal health status in farm animals.

INTRODUCTION: On discute depuis des années de l'usage des antibiotiques dans l'élevage des animaux de rente, en particulier en ce qui concerne leur utilisation incorrecte et la charge environnementale liée à des résidus d'antibiotiques susceptibles de favoriser l'apparition et la propagation de résistances. Toutefois les antibiotiques sont essentiels pour assurer une lutte efficace et durable contre les maladies d'origine bactérienne. Dans le but d'optimiser l'usage des antibiotiques dans l'élevage des animaux de rente et, par conséquence, de réduire le développement de résistances, AntibioticScout.ch propose une aide à la décision pour un usage prudent de ces substances ("prudent use"). Parallèlement, on attire l'attention sur les traitements adjuvants et sur les mesures de prévention. Des mesures visant à améliorer la santé et le bien-être des animaux en tenant compte des fondements d'une bonne pratique vétérinaire sont des instruments efficaces pour réduire l'usage des antibiotiques. Cette réduction indispensable doit donc être combinée avec des mesures de gestion adéquates dans les élevages. Ce sont en particulier l'hygiène et les conditions d'élevage correctes ainsi que la mise en place de mesures de biosécurité qui sont décisives pour l'optimisation de la santé des troupeaux.

Selective inhibition of TNFR1 reduces osteoclast numbers and is differentiated from anti-TNF in a LPS-driven model of inflammatory bone loss.

The treatment of autoimmune disorders has been revolutionised by the introduction of biologics such as anti-tumour necrosis factor (anti-TNF). Although in rheumatoid arthritis patients a bone sparing effect of anti-TNF has been shown, the mechanism is not fully understood. Anti-TNF molecules block tumour necrosis factor (TNF) and prevent signalling via both TNF receptor 1 (TNFR1; p55) and TNF receptor 2 (TNFR2; p75). However, signalling via TNFR2 is reported to have protective effects in a number of cell and organ systems. Hence we set out to investigate if pharmacological inhibition of TNFR1 had differential effects compared to pan-TNF inhibition in both an in vitro cell-based model of human osteoclast activity and an in vivo mouse model of lipopolysaccharide (LPS)-induced osteolysis. For the in vitro experiments the anti-human TNFR1 domain antibody (dAb) DMS5541 was used, whereas for the in vivo mouse experiments the anti-mouse TNFR1 dAb DMS5540 was used. We show that selective blocking of TNFR1 signalling reduced osteoclast formation in the presence of TNF. Subcutaneous LPS injection over the calvaria leads to the development of osteolytic lesions within days due to inflammation driven osteoclast formation. In this model, murine TNFR2 genetically fused with mouse IgG1 Fc domain (mTNFR2.Fc), an anti-TNF, did not protect from bone loss in contrast to anti-TNFR1, which significantly reduced lesion development, inflammatory infiltrate, and osteoclast number and size. These results support further exploring the use of TNFR1-selective inhibition in inflammatory bone loss disorders such as osteomyelitis and peri-prosthetic aseptic loosening.

Field-Based Planetary Protection Operations for Melt Probes: Validation of Clean Access into the Blood Falls, Antarctica, Englacial Ecosystem.

Subglacial environments on Earth offer important analogs to Ocean World targets in our solar system. These unique microbial ecosystems remain understudied due to the challenges of access through thick glacial ice (tens to hundreds of meters). Additionally, sub-ice collections must be conducted in a clean manner to ensure sample integrity for downstream microbiological and geochemical analyses. We describe the field-based cleaning of a melt probe that was used to collect brine samples from within a glacier conduit at Blood Falls, Antarctica, for geomicrobiological studies. We used a thermoelectric melting probe called the IceMole that was designed to be minimally invasive in that the logistical requirements in support of drilling operations were small and the probe could be cleaned, even in a remote field setting, so as to minimize potential contamination. In our study, the exterior bioburden on the IceMole was reduced to levels measured in most clean rooms, and below that of the ice surrounding our sampling target. Potential microbial contaminants were identified during the cleaning process; however, very few were detected in the final englacial sample collected with the IceMole and were present in extremely low abundances (∼0.063% of 16S rRNA gene amplicon sequences). This cleaning protocol can help minimize contamination when working in remote field locations, support microbiological sampling of terrestrial subglacial environments using melting probes, and help inform planetary protection challenges for Ocean World analog mission concepts.

TLR signalling and adapter utilization in primary human in vitro differentiated adipocytes.

Toll-like receptors (TLRs) are central to innate immunity and yet their expression is widespread and not restricted to professional inflammatory cells. TLRs have been reported on adipocytes and have been implicated in obesity-associated pathologies such as diabetes. Why TLRs are found on adipocytes is not clear although one hypothesis is that they may coordinate energy utilization for the energy intensive process of an immune response. We have explored TLR signalling in primary human in vitro differentiated adipocytes and investigated the specific adapter molecules that are involved. Only lipopolysaccharide (LPS), poly(I:C), Pam3CSK4 and MALP-2 could induce the production of IL-6, IL-8 and MCP-1 by adipocytes. Poly(I:C) alone caused a strong induction of type I interferons, as assessed by IP-10 production. Using siRNA, it was confirmed that LPS-dependent signalling in adipocytes occurs via TLR4 utilizing the adapter molecules MyD88, Mal and TRIF and caused rapid degradation of IκBα. Pam3CSK4 signalling utilized TLR2, MyD88 and Mal (but not TRIF). However, the response to poly(I:C) observed in these cells appeared not to require TRIF, but MyD88 was required for induction of NFκB-dependent cytokines by Poly(I:C). Despite this, IκBα degradation could not be detected in poly(I:C) stimulated adipocytes at any time-point up to 4 h. Indeed, IL-6 transcription was not induced until 8-16 h after exposure. These data suggest that Pam3CSK4 and LPS signal via the expected routes in human adipocytes, whereas poly(I:C)/TLR3 signalling may act via a TRIF-independent, MyD88-dependent route.

Pathogen dependent effects of high amounts of oxytocin on the bloodmilk barrier integrity during mastitis in dairy cows.

INTRODUCTION: The reduction of antibiotic use in food producing animals becomes increasingly important. Therefore, suitable alternatives for mastitis treatment in dairy cows have to be considered. Oxytocin (OT) induces milk ejection and hence supports milk removal from infected mammary quarters. Beyond udder emptying, the injection of very high dosages of OT causes increased somatic cell counts (SCC) in milk and enables the transfer of immunoglobulins (Ig) from blood into milk through a reduced blood-milk barrier integrity. The aim of the present study was to investigate pathogen-specific changes of SCC, the blood derived milk components lactate dehydrogenase (LDH), serum albumin (SA), and IgG in milk of cows suffering from mastitis caused by different pathogens treated with two intravenous injections of high dosages of OT (100 IU). Milk samples from 184 dairy cows from different farms were collected on day 1 (day of clinical examination and mastitis diagnosis) and on days 2, 3, 14, and 28. Bacteriological examination (day 1) identified involved pathogens. Cows were randomly assigned to treatment (OT injections on days 1 and 2) or control group (no OT). Independently of the assigned experimental group, cows received the common therapy protocol of the veterinary practice after sample collection if the general condition was affected. Milk SCC, LDH, SA, and IgG changed specifically depending on involved pathogens. Highest values of all three parameters were measured in mastitis caused by Streptococcus uberis. Changes were less pronounced with other Streptococci spp., Staphylococci spp. or Corynebacterium bovis. Oxytocin treatment did not affect any of the studied parameters independent of the involved pathogen. Only in quarters infected with Staphylococci other than Staphylococcus aureus a decreased SCC and increased IgG concentrations in quarters, where no pathogens were detected, were observed. Thus, high dosage OT administration is obviously not suitable as a stand-alone mastitis treatment in dairy cows.

INTRODUCTION: La réduction de l'utilisation d'antibiotiques chez les animaux destinés à l'alimentation devient de plus en plus importante. Par conséquent, des alternatives appropriées au traitement des mammites chez les vaches laitières doivent être envisagées. L'ocytocine (OT) induit l'éjection du lait et favorise donc l'élimination du lait des quartiers infectés. Au-delà de la vidange de la mamelle, l'injection de doses très élevées d'OT entraîne une augmentation du nombre de cellules somatiques (CSC) dans le lait et permet le transfert d'immunoglobulines (Ig) du sang vers le lait grâce à une réduction de l'intégrité de la barrière sang-lait. Le but de la présente étude était d'étudier les changements spécifiques aux agents pathogènes du CSC, les composants du lait dérivés du sang que sont la lactate déshydrogénase (LDH) et l'albumine sérique (SA) ainsi que les IgG dans le lait de vaches souffrant de mammites causées par différents agents pathogènes traités par deux injections intraveineuses de doses élevées d'OT (100 UI). Des échantillons de lait de 184 vaches laitières de différentes exploitations ont été prélevés au jour 1 (jour de l'examen clinique et diagnostic de mammite) et aux jours 2, 3, 14 et 28. L'examen bactériologique (jour 1) a identifié les agents pathogènes impliqués. Les vaches ont été assignées au hasard au traitement (injections d'OT les jours 1 et 2) ou au groupe témoin (pas d'OT). Indépendamment du groupe auquel elles étaient attribuées, les vaches ont reçu le protocole thérapeutique usuel du cabinet vétérinaire après le prélèvement de l'échantillon si leur état général était affecté. Le CSC, la LDH, la SA et les IgG du lait ont varié spécifiquement en fonction des agents pathogènes impliqués. Les valeurs les plus élevées des trois paramètres ont été mesurées dans les mammites causées par Streptococcus uberis. Les changements étaient moins prononcés avec d'autres Streptococci spp., Staphylococci spp. ou Corynebacterium bovis. Le traitement à l'ocytocine n'a affecté aucun des paramètres étudiés indépendamment de l'agent pathogène impliqué. On a uniquement observé, dans les mammites causées par des staphylocoques autres que Staphylococcus aureus, une diminution du CSC et, dans les mammites où aucun agent pathogène n'a été détecté, une augmentation des concentrations d'IgG dans les quartiers. Ainsi, l'administration d'OT à forte dose n'est pas appropriée comme traitement unique des mammites chez les vaches laitières.

A Uniform Description of Perioperative Brain MRI Findings in Infants with Severe Congenital Heart Disease: Results of a European Collaboration.

BACKGROUND AND PURPOSE: A uniform description of brain MR imaging findings in infants with severe congenital heart disease to assess risk factors, predict outcome, and compare centers is lacking. Our objective was to uniformly describe the spectrum of perioperative brain MR imaging findings in infants with congenital heart disease. MATERIALS AND METHODS: Prospective observational studies were performed at 3 European centers between 2009 and 2019. Brain MR imaging was performed preoperatively and/or postoperatively in infants with transposition of the great arteries, single-ventricle physiology, or left ventricular outflow tract obstruction undergoing cardiac surgery within the first 6 weeks of life. Brain injury was assessed on T1, T2, DWI, SWI, and MRV. A subsample of images was assessed jointly to reach a consensus. RESULTS: A total of 348 MR imaging scans (180 preoperatively, 168 postoperatively, 146 pre- and postoperatively) were obtained in 202 infants. Preoperative, new postoperative, and cumulative postoperative white matter injury was identified in 25%, 30%, and 36%; arterial ischemic stroke, in 6%, 10%, and 14%; hypoxic-ischemic watershed injury in 2%, 1%, and 1%; intraparenchymal cerebral hemorrhage, in 0%, 4%, and 5%; cerebellar hemorrhage, in 6%, 2%, and 6%; intraventricular hemorrhage, in 14%, 6%, and 13%; subdural hemorrhage, in 29%, 17%, and 29%; and cerebral sinovenous thrombosis, in 0%, 10%, and 10%, respectively. CONCLUSIONS: A broad spectrum of perioperative brain MR imaging findings was found in infants with severe congenital heart disease. We propose an MR imaging protocol including T1-, T2-, diffusion-, and susceptibility-weighted imaging, and MRV to identify ischemic, hemorrhagic, and thrombotic lesions observed in this patient group.

Induction of immunity and tolerance in vitro by hapten protein conjugates. 3. Hapten inhibition studies of antigen binding to B cells in immunity and tolerance.

The capacity of dissociated spleen cell suspensions to be immunized by dinitrophenylated polymeric flagellin (DNP POL), in the absence of thymus-dependent lymphocytes or macrophages, provided a simple experimental system to investigate the mechanism of binding of antigen molecules to nonthymus-dependent lymphocyte (B cell) receptors during the induction of immunity or tolerance. Various nonimmunogenic DNP compounds were used to inhibit the anti-DNP response to DNP POL. By performing inhibition experiments of brief duration at 4 degrees C, it was established that the inhibition of the anti-DNP response by nonimmunogenic compounds was due to competitive blockade of receptors, and not tolerance or receptor modulation. It was found that univalent DNP compounds were much less efficient inhibitors of the antibody response than multivalent DNP conjugates. The difference in inhibitory capacity between univalent and multivalent DNP human globulin (DNP HgG) suggested the importance of interaction with both combining sites of a single receptor antibody molecule. Nonimmunogenic highly conjugated DNP(3)POL was a more efficient inhibitor of the anti-DNP response to immunogenic DNP(1)POL than DNP(12)HgG, indicating that interactions at more than one receptor molecule are involved in immunization of B cells. Recent demonstrations of the rapid metabolic turnover of receptor antibody molecules suggests that the requirement for multipoint binding (to different receptors) may simply be to maintain the antigen at the cell surface in a dynamic system. Competitive inhibition experiments were also performed to investigate the mechanism of binding of DNP(3)POL in the induction of B cell tolerance. It was found that monovalent DNP compounds or multivalent DNP(12)HgG did not prevent the induction of tolerance, unlike their capacity to inhibit immunity, suggesting that a tolerance-inducing antigen binds more avidly to the cell membrane than an immunogen. The inhibition data obtained here, together with prior results describing the differential immunogenicity of DNP conjugates of different structure, and the importance of epitope density on DNP POL conjugates, permit certain conclusions about the details of antigen-receptor interaction in immunity and tolerance. Distinctions between the mechanisms of immune and tolerance induction are discussed.

Induction of immunity and tolerance in vitro by hapten protein conjugates. I. The relationship between the degree of hapten conjugation and the immunogenicity of dinitrophenylated polymerized flagellin.

Of many dinitrophenylated (DNP) protein conjugates tested, only DNP conjugated to polymerized flagellin (DNP-POL) (or the structurally related bacterial flagella) elicited a primary anti-DNP response in vitro. Other DNP proteins, such as DNP-monomeric flagellin (DNP-MON), were capable of inducing secondary responses in vitro. The capacity of DNP-POL to immunize spleen cell suspensions devoid of thymus-derived cells was the reason for the greater immunogenicity of DNP-POL, since even large numbers of flagellin-reactive activated thymus cells did not increase the anti-DNP response of normal spleen cells immunized with DNP-POL, whereas the thymus-dependent response to DNP-MON was markedly increased. The capacity of various batches of DNP-POL to immunize normal spleen cells in vitro varied markedly, depending on the number of DNP groups conjugated. DNP-POL with few DNP groups conjugated was immunogenic, but even at very high concentrations did not induce tolerance. In contrast, highly conjugated DNP-POL did not immunize, but readily induced tolerance. DNP-POL with intermediate degrees of conjugation were, like unconjugated polymeric flagellin, capable of inducing both immunity and tolerance. Since DNP-POL immunizes bone marrow-derived lymphocytes (B cells) directly the reduced response was not due to a masking of carrier determinants, necessary for cell collaboration. By using mixed DNP-5-(dimethylamino)-1-naphthalyl (dansyl)-POL conjugates, it was found that the inhibitory effect of a high degree of hapten conjugated was hapten specific. Depolymerization of DNP-POL to DNP-MON, which does not induce primary anti-DNP responses, was excluded by centrifugation analysis and electron microscopy. The relationship of the degree of hapten conjugation on DNP-POL to the capacity to induce tolerance and immunity in B cells has clarified the mechanism of immunological triggering of these cells. A model of the mechanism of "signal" discrimination between immunity and tolerance in B cells, based on these findings, is proposed.

Cell interactions in the immune response in vitro. V. Specific collaboration via complexes of antigen and thymus-derived cell immunoglobulin.

The mechanism of interaction of T and B lymphocytes was investigated in an in vitro hapten carrier system using culture chambers with two compartments separated by a cell impermeable nucleopore membrane. Because specific cell interaction occurred efficiently across this membrane, contact of T and B lymphocytes was not essential for cooperation which must have been mediated by a subcellular component or "factor." By using different lymphoid cell populations in the lower culture chamber and activated thymus cells in the upper chamber (with antigen present in both), it was found that the antigen-specific mediator acted indirectly on B cells, through the agency of macrophages. Macrophages which had been cultured in the presence of activated T cells and antigen acquired the capacity to specifically induce antibody responses in B cell-containing lymphoid populations. Trypsinization of these macrophages inhibited their capacity to induce immune responses, indicating that the mediator of cell cooperation is membrane bound. By using antisera to both the haptenic and carrier determinants of the antigen as blocking reagents, it was demonstrated that the whole antigen molecule was present on the surface of macrophages which had been exposed to activated T cells and antigen. Because specifically activated T cells were essential a component of the antigen-specific mediator must be derived from these cells. By using anti-immunoglobulin sera as inhibitors of the binding of the mediator to macrophages, the T cell component was indeed found to contain both kappa- and micro-chains and was thus presumably a T cell-derived immunoglobulin. It was proposed that cell cooperation is mediated by complexes of T cell IgM and antigen, bound to the surface of macrophage-like cells, forming a lattice of appropriately spaced antigenic determinants. B cells become immunized by interacting with this surface. With this mechanism of cell cooperation, the actual pattern of antigen-B cell receptor interactions in immunization would be the same with both thymus-dependent and independent antigens. An essential feature of the proposed mechanism of cell cooperation is that macrophage-B cell interaction must occur at an early stage of the antibody response, a concept which is supported by many lines of evidence. Furthermore this mechanism of cell interaction can be elaborated to explain certain phenomena such as the highly immunogenic macrophage-bound antigen, antigenic competition, the distinction between immunity and tolerance in B lymphocytes, and the possible mediation of tolerance by T lymphocytes.

Cell interactions in the immune response in vitro. II. The requirement for macrophages in lymphoid cell collaboration.

The requirement for macrophages in thymus-dependent antibody responses was studied in vitro. Three different macrophage-deficient cell populations were studied: spleen cells passed through a glass bead column at 37 degrees C, spleen cells cultured with specific antimacrophage serum, and thoracic duct lymphocytes. These cell populations from mice primed to dinitrophenylated (DNP) fowl gamma globulin were unable to respond to the homologous conjugate in vitro. DNP-reactive B cells were present in normal proportions, since all three macrophage-depleted populations responded normally to macrophage-independent and thymus-independent DNP flagella. Carrier-reactive T cells were present, as the helper capacity of carrier-primed spleen cells was the same as carrier-primed lymphocytes, and thoracic duct lymphocytes are a well-established source of helper cells. The inhibition of the cooperative response was thus due to removal of macrophages, and this was proven by restoration of thymus-dependent anti-DNP responses by small numbers of anti-theta-treated peritoneal exudate cells. These results suggest that macrophages are essential in cell collaboration, While their exact function in cell collaboration is not yet known, the above observation suggests that the mechanism of T-B collaboration involves the surface of macrophages.

Suppressor-cell induction in vitro. IV. Target of antigen-specific suppressor factor and its genetic relationships.

Antigen-specific suppressor factor produced by metabolically active in vitro-induced suppressor cells, upon further antigenic stimulation, act on nylon wool nonadherent, Ly-2-negative target cells within helper cell population, resulting in suppression of both the IgM and IgG antibody responses. Thus the target is an Ly-1+ T cell, possibly the helper cell. All the mouse strains tested so far have been able to produce the factor, and when tested in CBA or B10 mice, there seems to be no genetic restriction involved e.g., nonsyngeneic suppressor factors suppress as well as do the syngeneic factors. Comparison of the properties of suppressor factor with those of extracts of suppressor cells yield differences in origin, target of action and effect, indicating that these are different molecules. The heterogeneity of suppressor pathways is discussed.

Antibody-mediated suppression of the immune response in vitro. I. Evidence for a central effect.

Antibody-mediated suppression of the in vitro immune response to polymerized flagellin of Salmonella adelaide and to sheep erythrocytes was studied at the cellular level. Normal mouse spleen cells, preincubated in vitro with mixtures of antigen and antibody for short periods of time before being washed, did not respond to an optimal antigenic challenge in vitro, whereas similar cells treated with antibody alone gave a normal response. The degree of immune suppression was found to depend on the time of preincubation. Significant immune suppression could be induced in as short a time as 15 min, whereas profound suppression (90%) required the incubation of cells with mixtures of antigen and antibody for 4-6 hr. Mouse spleen cells treated similarly were also unable to respond subsequently to the antigen upon transfer to lethally irradiated hosts, as measured at both the level of the antigen-reactive cell and that of serum antibody production. These results were taken as evidence that in vitro an effect of antibody-mediated suppression occurred at the level of the immunocompetent cell. Similarities between immune tolerance and antibody-mediated suppression in vitro were described, and the significance of the findings discussed in the light of current concepts of the mechanism of antibody-mediated suppression.

Antibody-mediated suppression of the immune response in vitro. II. A new approach to the phenomenon of immunological tolerance.

Immunological tolerance to H antigens of Salmonella adelaide may be induced in vitro by the exposure of mouse spleen cells for 6 hr to an immunogenic dose of polymerized flagellin in the presence of low concentrations of specific antibody. Such antibody-mediated tolerance requires an optimal antigen: antibody ratio for its induction. A shift in this ratio in favor of the antibody concentration results in failure of tolerance induction and leads to immune suppression commonly known as antibody-mediated feedback inhibition which is not analogous to immunological tolerance. Fragment A of flagellin fails to induce immunological tolerance in vitro. Tolerance to polymerized flagellin may however be induced in vitro, provided the spleen cells are exposed to fragment A in the presence of specific antibody for 6 hr. The results are discussed in the light of current theories of the mechanism of tolerance induction.

The relationship between antigenic structure and the requirement for thymus-derived cells in the immune response.

Certain antigens such as polymerized flagellin are capable of producing relatively normal antibody levels in thymectomized mice, whereas others, including heterologous erythrocytes require the presence of T cells in a helper capacity. The mechanism of thymus-independent antibody production was investigated by comparing the primary IgM responses of spleen cells from ATXBM, XBM, and normal mice to various physical forms of the flagellar antigens of Salmonella adelaide in vitro. No reduction in antibody-forming cell levels to polymerized flagellin over a wide dose range was observed in ATXBM cultures, although the same spleen cells did not respond to an optimal dose of sheep red cells. In contrast, when flagellar determinants were presented in a monomeric form or as flagellin-coated donkey red cells, a highly significant difference was observed between the antibody responses of spleen cells from ATXBM mice and XBM or normal controls. The results suggested that the requirement for T cells in antibody production is not a property of specific antigenic determinants, but depends on the mode of antigenic presentation. The validity of this conclusion was confirmed by using another antigenic determinant (DNP) coupled either to the thymus-independent carrier, POL, or to the thymus-dependent carrier, DRC. Spleen cells from XBM mice produced comparable AFC levels to both forms of DNP, but the results from ATXBM cultures showed a marked difference. The anti-DNP response to DNP-DRC was greatly reduced compared to controls, whereas that to DNP-POL was normal even after prolonged thoracic duct drainage of the ATXBM donors and pretreatment of their spleen cells with anti-theta-serum and complement. The data presented here imply that the role of T cells in humoral immunity is the presentation of antigen to B cells in such a manner as to initiate optimal antibody synthesis.

The role of macrophages in the generation of T-helper cells. II. The genetic control of the macrophage-T-cell interaction for helper cell induction with soluble antigens.

Helper cell induction to nonparticle antigens in vitro requires the cooperation of T cells and macrophages, but does not occur if the macrophages are allogenic. The reasons for this were investigated. Malfunction of allogenic macrophages was excluded by cultures with their syngenic T cells; suppressor cell induction was excluded by admixture experiments. Thus, T cells and macrophages only cooperated if they were genetically similar. The genetic locus (loci) involved was mapped. Using congenic lines differing only at the H-2 complex, the genetic control of T-macrophage interaction was localized in the H-2 region. Mice with intra H-2 recombinants were used to map the T-macrophage interaction locus in the I-A region of the H-2 complex (formerly known as poly-D, L-ala-poly-L-lys. Recombinants were also used to exclude the presence of another T-macrophage locus either the K, I-B, or I-C, SS-Slp, or D regions of the H-2 complex. Genetic restrictions for T-macrophage interaction in helper cell induction was shown in mice of the H-2-k, d, b, q, s genotypes as well as in H-2 recombinants. The possible mechanisms and significance of this genetic restriction are discussed.

Cell interactions in the immune response in vitro. 3. Specific collaboration across a cell impermeable membrane.

Tissue cultures with two compartments, separated by a cell impermeable nuclepore membrane (1 micro pore size), were used to investigate the mechanism of T-B lymphocyte cooperation. It was found that collaboration was as effective when the T and B lymphocyte populations were separated by the membrane as when they were mixed together. Critical tests were performed to verify that the membranes used were in fact cell impermeable. The specificity of the augmentation of the B cell response by various T cell populations was investigated. Only the response of B cells reactive to determinants on the same molecule as recognized by the T cells was augmented markedly. Specific activation of thymocytes by antigen was necessary for efficient collaboration across the membrane. The response of both unprimed and hapten-primed spleen cells was augmented by the T cell "factor" although, as expected, hapten-primed cells yielded greater responses. The T cell factor acted as efficiently if T cells were present or absent in the lower chamber. Thus the site of action of the T cell factor was not on other T cells, but was either on macrophages or the B cells themselves. The T cell-specific immunizing factor did not pass through dialysis membranes. The experiments reported here help rule out some of the possible theories of T-B cell collaboration. Clearly T-B cell contact was not necessary for successful cooperation to occur in this system. Possible theoretical interpretations of the results and their bearing on the detailed mechanism of T-B lymphocyte cooperation are discussed.

Cell interactions in the immune response in vitro. IV. Comparison of the effects of antigen-specific and allogeneic thymus-derived cell factors.

The role of soluble factors in cell collaboration was investigated by means of a tissue culture system in which populations of T and B cells were either incubated together or separated from each other by cell impermeable membranes. Histoincompatible T cells were found to augment antibody responses to both thymus-dependent and thymus-independent antigens, whether they were in contact with B cells or not. The properties of the factor released by the T cells in the allogeneic mixture were compared with those of the previously reported antigen-specific mediator found in syngeneic collaborative antibody responses. Unlike the latter, the factor made in allogeneic responses failed to display any degree of antigen specificity either in its induction or in its action, enhancing responses to all the antigens present in the cultures to a similar degree. It was of lower molecular weight than the antigen-specific factor, because it could pass through dialysis membranes as well as nuclepore membranes, whereas the antigen-specific factor could only penetrate nuclepore membranes. Furthermore, the factor made in allogeneic reactions had a different site of action. It acted directly on B lymphocytes, whereas the antigen-specific component acts through macrophages. Although antigen in the presence of the allogeneic factor did not initiate antibody production, it augmented responses once they had been induced by a matrix of antigenic determinants, either mediated by the antigen-specific factor or directly by a thymus-independent antigen. It was therefore considered to act at a later stage of the antibody response, probably as a nonspecific stimulator of immune B cell proliferation. Observations that the effect on the allogeneic factor are more pronounced 2 days after the beginning of the response are in keeping with this interpretation.

Dendritic cells induce T cell proliferation to synthetic antigens under Ir gene control.

Dendritic cells prepared by a modification of the method of Steinman and Cohn are I-A+ and FcR-. They are extremely potent at activating not only allogeneic T cell proliferation but also antigen-specific syngeneic T cell proliferation. Dendritic cells from nonresponder strains are unable to present antigens to responder X nonresponder T cells, suggesting that they may be a site of Ir gene product expression.

Nature of T-cell macrophage interaction in helper-cell induction in vitro. II. Two stages of T-helper-cell differentiation analyzed in irradiation and allophenic chimeras.

The genetic restriction in the T-cell-macrophage-like cell interaction in helper cell induction was investigated with allophenic and irradiation chimeras of various types. Using T cells from P leads to F1 chimeras, there was a restriction of cooperation with the parental haplotype accessory cells, unless the chimeric mice were repopulated with macrophages of the opposite haplotype before priming. T cells from primed or unprimed F1 leads to P chimeras only cooperated with recipient type accessory cells. These observations led to the hypothesis that there are two stages in the genesis of immunocompetence of T helper cells, one dependent on the thymus, and the other on peripheral macrophage-like cells. Purified T cells from P1 + P2 leads to F1 irradiation chimeras behaved in an unexpected manner in the unprimed state, preferring to cooperate with their own haplotype macrophages. This self preference was lost after antigen priming in vivo and was not noted in allophenic chimeras. This loss of self preference was restricted to the haplotypes represented in the chimeras, and did not extend to third party haplotypes. While these in vitro induced helper cells from chimeric mice show clear genetic restrictions at the T-cell macrophage-like cell interaction, there was no evidence for a matching T-B genetic restriction.

Platelet-derived interleukin 1 induces human endothelial adhesion molecule expression and cytokine production.

Interleukin 1 (IL-1) plays a central role in the regulation of the body's response to infectious and inflammatory stimuli. Recent evidence has shown that human platelets express a cell associated form of this proinflammatory cytokine very rapidly following activation. Since one of the earliest events in inflammation is frequently the rapid adhesion of platelets to injured endothelium, it was of interest to determine whether platelets express IL-1 in a functionally relevant form that can alter the phenotype of human endothelial cells in vitro. Thrombin activated platelets induced significant expression of the adhesion molecule intercellular adhesion molecule 1, as well as secretion of the IL-1 inducible cytokines IL-6 and granulocyte macrophage colony stimulating factor by cultured human umbilical cord and saphenous vein endothelial cells. This was inhibited by prior treatment of the platelets with antibody specific for IL-1. These results suggest that platelet delivered IL-1 might initiate and regulate some of the earliest phases of the inflammatory response. An additional observation of interest was differential induction of endothelial leucocyte adhesion molecule 1 by activated platelets on saphenous vein but not umbilical vein but not umbilical vein endothelial cells, which suggests functional heterogeneity of the endothelial cells.