Responses of pigs to a re-challenge with Actinobacillus pleuropneumoniae after being treated with different antimicrobials following their initial exposure.

Four groups of six specific pathogen-free (SPF) pigs were inoculated intranasally with Actinobacillus pleuropneumoniae serotype 2 and treated with either enrofloxacin, tetracycline or penicillin at the onset of clinical disease, or left untreated. A fifth group was left uninoculated. The inoculated control and the penicillin-treated groups developed severe disease, but the groups treated with enrofloxacin and tetracycline recovered rapidly. All the inoculated pigs, except those treated with enrofloxacin developed serum antibodies to A pleuropneumoniae. On day 28, all five groups were challenged with A pleuropneumoniae without any subsequent treatment. The previously uninoculated control group and the enrofloxacin-treated group developed severe disease, but the three seropositive groups remained unaffected.

Postweaning multisystemic wasting syndrome (PMWS) in Sweden from an exotic to an endemic disease.

Postweaning multisystemic wasting syndrome (PMWS) is causally associated with porcine circovirus type 2 (PCV2) infection of pigs. PCV2 was first demonstrated in Swedish pigs in 1993, although the virus was almost certainly present in pigs in the country before that. Despite this, no signs of PMWS were observed in pigs of Sweden until the first outbreak was reported in 2003. The accumulated number of PMWS-affected herds have increased via 16 (2004) and 41 (2005) to 123 in December 2006. Of these herds, 30 (25%) have now been declared free from PMWS. However, a number of other herds have had individual pigs that have fulfilled the demands for PMWS at necropsy and 52 of these herds have been declared negative on herd basis after treatment for intestinal or respiratory diseases, and/or by correcting shortcomings in management of the herd including feed. Thus, individual cases of the disease have been observed in around 200 herds by the end of 2006 and PMWS is now regarded as an endemic disease in Sweden. The pig population of Sweden is geographically isolated, the density of pigs and the pathogen load in the country is low and the use of growth promoters (low dose antibiotics in feed) was prohibited in 1986. Additionally, the trade of animals in Sweden is organised in a restricted way. Because of these factors it is possible to conduct meaningful real-time studies on the transformation of PMWS in Sweden from being an exotic to an endemic disease in a three year time scale. Initially the PMWS cases were concentrated in the southern part of Sweden, but have gradually spread north. The PMWS-positive herds have, in general, had an effective production, but some management errors have constantly been observed in affected herds. Physical links between affected herds are often missing, and the data generated to date on the PMWS outbreaks in Sweden do not suggest an introduction of a new contagious microbe into the country that is responsible for the PMWS outbreaks, nor does PMWS appear to be spread via semen. In Sweden, intensity in rearing, disease preventing measures and immaturity of the piglets appear to be important as predisposing factors to PMWS and, as such, are discussed in this article.

Stranded seed displacement, migration, and loss after permanent prostate brachytherapy as estimated by Day 0 fluoroscopy and 4-month postimplant pelvic x-ray.

PURPOSE: The aim of the study was to determine the incidence of local displacement, distant seed migration to the chest, and seed loss after permanent prostate brachytherapy (PPB) with stranded seeds (SSs) using sequential two-dimensional fluoroscopic pelvic and chest x-rays. METHODS AND MATERIALS: Between October 2010 and April 2014, a total of 137 patients underwent PPB and 4-month followup pelvic and chest x-ray imaging. All patients had exclusively SSs placed and an immediate postimplant fluoroscopic image of the seed cluster. Followup x-ray images were evaluated for the number, location, and displacement of seeds in comparison to Day 0 fluoroscopic images. Significant seed displacement was defined as seed displacement >1 cm from the seed cluster. Followup chest x-rays were evaluated for seed migration to the chest. RESULTS: Seed migration to the chest occurred in 3 of the 137 patients (2%). Seed loss occurred in 38 of the 137 patients (28%), with median loss of one seed (range, 1-16), and total seeds loss of 104 of 10,088 (1.0%) implanted. Local seed displacement was seen in 12 of the 137 patients (8.8%), and total seeds displaced were 0.15% (15/10,088). CONCLUSIONS: SS placement in PPB is associated with low rates of substantial seed loss, local displacement, or migration to the chest. Comparing immediate postimplant fluoroscopic images to followup plain x-ray images is a straightforward method to supplement quality assurance in PPB and was found to be useful in identifying cases where seed loss was potentially of clinical significance.

Experimental reproduction of postweaning multisystemic wasting syndrome (PMWS) in pigs in Sweden and Denmark with a Swedish isolate of porcine circovirus type 2.

An experimental model using 3-day-old snatch-farrowed colostrum-deprived piglets co-infected with porcine circovirus type 2 (PCV2) and porcine parvovirus (PPV) is at present one of the best methods to study factors affecting development of postweaning multisystemic wasting syndrome (PMWS). A Swedish isolate of PCV2 (S-PCV2) retrieved in 1993 from a healthy pig has been used in this model to reproduce PMWS in pigs from Northern Ireland. This virus has been present in the Swedish pig population for at least a decade without causing any known PMWS disease problems, despite its potential pathogenicity. The reasons for this are unknown, but could be related to genetics, absence of triggers for PCV2 upregulation (infectious agent and/or management forms) within Swedish pig husbandry. In order to confirm the pathogenicity of S-PCV2, Swedish and Danish pigs were experimentally infected with this isolate according to the established model. Swedish pigs were also infected with a reference isolate of PCV2 (PCV2-1010) to compare the severity of disease caused by the two isolates in Swedish pigs. Both Danish and Swedish pigs developed PMWS after the experimental infection with S-PCV2. Antibodies to PCV2 developed later and reached lower levels in serum from pigs infected with S-PCV2 than in pigs inoculated with PCV2-1010. In general, pigs infected with S-PCV2 showed more severe clinical signs of disease than pigs infected with PCV2-1010, but pigs from all PCV2-inoculated groups displayed gross and histological lesions consistent with PMWS. All pigs inoculated with PPV, alone or in combination with PCV2, displayed interleukin-10 responses in serum while only pigs infected with PPV in combination with PCV2 showed interferon-alpha in serum on repeated occasions. Thus, the pathogenicity of S-PCV2 was confirmed and a role for cytokines in the etiology of PMWS was indicated.

Lectins inhibit the Aujeszky's disease virus-induced interferon-alpha production of porcine peripheral blood mononuclear cells.

The interaction between virus and peripheral blood mononuclear cells (PBMC) required to elicit the production of interferon-alpha (IFN-alpha) by the so-called natural interferon-producing cell is unknown. However, results from inhibition experiments suggest that viral glycoproteins are essential in this IFN induction process. We demonstrate here that cellular glycoproteins also appear to be involved in the initiation of IFN-alpha production. Lectins, that is, sugar binding glycoproteins, inhibited the Aujeszky's disease virus-induced IFN-alpha production of porcine PBMC by up to 99%. The level of inhibition varied with lectin used (concanavalin A, Galanthus nivalis lectin, Helix pomatia lectin, and lentil lectin). Preincubation experiments with porcine cells and concanavalin A (ConA) revealed that the lectin exerted its major effect directly on the PBMC. Although the IFN-alpha production in some cases was reduced by more than 90%, the PBMC were still able to proliferate in response to mitogenic lectins. The ConA-mediated inhibition of the IFN-alpha production was reduced if the lectin was added later than 6-8 h after the start of induction and was not mediated by soluble factors. Both orthovanadate and staurosporine inhibited the IFN-alpha production and did not relieve the ConA-mediated inhibition. Thus, ConA seems to interfere with the early events during IFN-alpha induction, but the mechanisms behind this interference could not be clarified.

Evaluation of flow cytometry and fluorescence microscopy for the estimation of bovine mononuclear phagocytes.

Bovine blood mononuclear cells were isolated by density gradient centrifugation on Ficoll-Paque. Phagocytic mononuclear cells were characterized functionally by ingestion of fluorescent latex beads. After incubation with beads the cells were treated with Triton X-100 and propidium iodide (PI) to stain DNA. Cells were analyzed with a FACS-III instrument connected to a Nuclear Data-6660 multiparameter computer system. The computer was used to evaluate the 2 parameter histograms in order to enumerate the percentage of cells with different numbers of associated beads. With this system we also obtained information about cell concentration and number of beads per cell. Results from flow cytometry and manual counting by fluorescence microscopy were compared and good correlation (r = 0.91) was obtained. During the first hours of incubation latex beads adhered to cell surfaces as demonstrated by FCM histograms and fluorescence microscopy. Blood mononuclear phagocytes have to be incubated for several hours before significant phagocytotic activity can be detected.

Monoclonal antibodies to salmonid immunoglobulin: characterization and applicability in immunoassays.

Monoclonal antibodies to rainbow trout (Oncorhynchus mykiss) IgM were prepared and characterized for use in immunoassays. Antibodies produced by the five clones reacted with the heavy chain of the immunoglobulin. No indication of different heavy chain isotype specificity was observed for the MAbs. One clone discerned IgM from rainbow trout while the other four clones cross-reacted with IgM from Atlantic salmon (Salmo salar) and from brown trout (Salmo trutta). The monoclonal antibodies identified a B-cell like lymphocyte population that contributed to approximately 45% of the blood leucocytes in rainbow trout but was absent in the thymus. The proportion of Ig+ cells was higher in blood lymphocyte cultures stimulated with lipopolysaccharide than in nonstimulated cultures or in cultures stimulated with Concanavalin A. Applied in an ELISA for measuring humoral antibodies to Vibrio anguillarum in trout, the monoclonal anti-rainbow trout IgM antibodies discriminated seropositive fish from control fish more efficiently than did polyclonal rabbit antitrout IgM antibodies.

Bovine virus diarrhoea virus induces in vitro a proliferative response of peripheral blood mononuclear cells from cattle immunized by infection.

The ability of bovine peripheral blood mononuclear cells (PBMC) to mount a proliferative response to bovine virus diarrhoea virus (BVDV) in vitro was examined. After culturing PBMC in the presence of a non-cytopathic strain of BVDV for 6 days, the magnitude of PBMC proliferation was measured as incorporation of radiolabelled thymidine, present during the last 18 h. Live, but not heat-inactivated, BVDV evoked a proliferative response of PBMC obtained from cattle seropositive to the virus. However, PBMC from seronegative or persistently BVDV-infected animals were not stimulated by BVDV. The presence of live BVDV did not alter the proliferative response of PBMC to stimulation with concanavalin A.

In vitro stimulation of antibody production to Mycoplasma hyopneumoniae by porcine peripheral blood mononuclear cells.

A method to stimulate and detect the in vitro production of antibodies to Mycoplasma hyopneumoniae by porcine peripheral blood mononuclear cells (PBMC) was established. PBMC were cultured in microtiter plates coated with a sonicated M. hyopneumoniae whole cell antigen and the amount of antibody bound to the coating antigen was determined by an enzyme linked immunosorbent assay (ELISA). In addition, the amount of non-bound antibody was determined by testing the culture supernatants in the ELISA which detects porcine antibodies to M. hyopneumoniae. The production of antibodies, in terms of total absorbance values, was enhanced by including 2.5 ng pokeweed mitogen (PWM) per ml growth medium without altering the specificity of the assay. In a pilot experiment, the applicability of the method to follow the development of antigen-reactive cells during primary and secondary immunizations with M. hyopneumoniae was evaluated. Antigen-reactive cells, identified by their ability to produce antibodies to M. hyopneumoniae in vitro, were detected seven days after the primary immunization and reached their highest antigen reactivity one week later. In comparison, antigen-reactive cells could be detected three days after the booster immunization and remained in the circulation for 2 weeks.

In vitro production of antibodies to bovine virus diarrhoea virus by peripheral blood mononuclear cells from cattle immunized by infection.

A method for in vitro production of antibodies to bovine virus diarrhoea virus (BVDV) by peripheral blood mononuclear cells (PBMC) was developed. The PBMC were cultured in microtitre plates coated with detergent-solubilized BVDV and the supernatants were tested in an enzyme-linked immunosorbent assay which detects IgG antibodies to BVDV. Following incubation of PBMC with an optimal concentration of pokeweed mitogen for 5 days, antibodies to BVDV were detected in culture supernatants of PBMC from immune cattle, but not in supernatants of PBMC from seronegative cattle, from persistently BVDV-infected cattle or from a 5-day-old calf that received BVDV antibodies via colostrum. This antibody-production assay may therefore be used as a tool to discriminate between passively acquired antibodies and those actively induced.

Effects of an experimental infection with Actinobacillus pleuropneumoniae on the interferon-alpha and interleukin-6 producing capacity of porcine peripheral blood mononuclear cells stimulated with bacteria, virus or plasmid DNA.

The effect of a bacterial infection on interferon-alpha (IFN-alpha) and interleukin-6 (IL-6) production by porcine cells was studied in specific pathogen-free (SPF) pigs, infected intranasally with Actinobacillus pleuropneumoniae serotype 2. Three experimental groups of five pigs were used: infected non-treated pigs, infected pigs that were treated with enrofloxacin at disease onset, and non-infected, non-treated control pigs. Blood samples were collected from all pigs on the day of infection and on days 1, 4, 7, 13 and 17 post-infection. Sera were analysed for presence of antibodies to A. pleuropneumoniae and for the cytokines IL-6 and IFN-alpha. Ability to produce these cytokines was tested in vitro using whole blood cultures stimulated with inactivated virus (Aujeszky's disease virus infected porcine kidney cells (ADV/PK-15)), inactivated bacteria (A. pleuropneumoniae) or bacterial plasmid (pcDNA3). All cytokine inducers were used neat or pre-incubated with the transfectious agent lipofectin. IL-6 appeared in the serum of all infected non-treated animals but no IFN-alpha was found in the serum of any of the experimental pigs. Accordingly, the bacteria induced a substantial IL-6 but hardly any IFN-alpha production when tested in vitro. However, following incubation with lipofectin, the inactivated bacteria as well as pcDNA3 became efficient inducers of IFN-alpha in whole blood cultures. The increased IFN-alpha production, previously recorded in vitro during the acute phase of infection with A. pleuropneumoniae, was confirmed using lipofected plasmid DNA and it was indicated that leukocytes obtained from infected but apparently cured animals also exhibited an increased production of IFN-alpha. Thus, even mild/sub-clinical bacterial infections may affect cytokine production in pigs.

Interleukin 6, serum amyloid A and haptoglobin as markers of treatment efficacy in pigs experimentally infected with Actinobacillus pleuropneumoniae.

The possibility to use acute phase proteins to monitor the elimination of a bacterial infection in pigs would facilitate an objective assessment of treatment with various antimicrobial substances. To examine this possibility, the acute phase response (IL-6, serum amyloid A (SAA), and haptoglobin) elicited by Actinobacillus pleuropneumoniae and its reduction on treatment with various antibiotics was studied in serum from specific pathogen free (SPF) pigs. Pigs were infected intranasally with A. pleuropneumoniae serotype 2, and either left as non-treated control pigs or treated with different antibiotics intramuscularly at onset of respiratory disease (20h post-infection). Pigs responded to the infection with prominent increases in activity and concentrations of IL-6, SAA, and haptoglobin. These responses were to a certain extent overlapping and covered the time span from a few hours after infection until development of detectable levels of specific antibodies (7-10 days post-infection in untreated pigs). The haptoglobin response lasted until the end of the study on day 17 and thereby partly coincided with the antibody response. Treatment with antimicrobials that effectively reduced establishment of the infection with A. pleuropneumoniae also reduced the duration of all three acute phase responses, and reduced the concentration of serum haptoglobin. In contrast, less efficacious treatments did not reduce these acute phase responses. Thus, acute phase reactants can be applied to monitor therapeutic effects of antimicrobial drugs in the pig and measurements of IL-6, SAA and haptoglobin could add valuable information about the stage of infection during a disease outbreak.

Humoral immune responses to Mycoplasma hyopneumoniae in sows and offspring following an outbreak of mycoplasmosis.

Previously healthy sows, seropositive to Mycoplasma hyopneumoniae, developed clinical signs of mycoplasmosis, as well as increasing amounts of antibodies to M. hyopneumoniae during an outbreak of the disease in a herd. During the early phase of the outbreak, young piglets (2 weeks) with maternal antibodies remained healthy while older seronegative piglets (4-7 weeks) developed the disease. The duration of the maternal antibodies to M. hyopneumoniae varied between litters and was related to the amount of antibodies in the serum of the dam. In sows, the level of serum antibodies decreased continuously from 4 weeks ante partum to partus, and the level of antibodies in the whey of colostrum was comparable to that in serum 4 weeks ante partum. After loss of maternal antibodies to M. hyopneumoniae, seropositive animals were not found among piglets younger than 9 weeks. Therefore peripheral blood mononuclear cells (PBMC) were collected from various age categories of piglets in order to measure the ability to produce antibodies to M. hyopneumoniae in vitro. PBMC obtained from piglets aged 1 and 3 weeks produced few antibodies to M. hyopneumoniae. Significantly higher levels of antibodies to M. hyopneumoniae were produced by PBMC obtained from pigs aged 5-9 weeks. Thus, the ability of PBMC to produce antibodies to M. hyopneumoniae in vitro seemed to be age-dependent.

Experimental reproduction of winter dysentery in lactating cows using BCV -- comparison with BCV infection in milk-fed calves.

Infection models were developed for adult cows and for young calves using the same strain of bovine coronavirus (BCV), which for the first time allows experimental reproduction of winter dysentery (WD) in seronegative lactating cows. The cattle were infected through direct contact with an experimentally inoculated calf. All experimental cattle shed faecal BCV with development of diarrhoea, being profusely watery with small amounts of blood in the most severely affected animals, including both cows and calves. The cows, in contrast to the calves, showed depressed general condition and appetite leading to a marked decrease in milk yield. Further age-associated differences were a shorter incubation period in the two youngest calves, but with milder fever and milder decrease in white blood cell counts. These findings shed light on the apparent epidemiological differences between WD and calf BCV diarrhoea suggesting that, (1) the same strains of BCV cause natural outbreaks of calf diarrhoea and WD, (2) seronegative cows are more severely affected by the infection than seronegative conventionally reared calves, and (3) unaffected general condition in diarrhoeic calves may lead to underestimation of the occurrence of calf diarrhoea in WD outbreaks. In response to infection, all cattle produced early interferon type 1 in serum and, except for one calf, in nasal secretions. A finding not previously reported is the detection of interferon type 1 responses in bovine milk. All cattle developed high IgM antibody responses and long-lasting IgA antibody responses both systemically and locally. The serum IgM antibody responses came earlier in most of the calves than in the cows. Prolonged IgM antibody responses were detected in serum and milk, while those in nasal secretions were much shorter. BCV-specific IgA was present in nasal secretions from all cattle throughout the 6 months follow-up. The IgA antibody response in serum was detected up to 17 months post-infection and the duration showed an age-related variation indicating a more prominent IgA memory in the adult cattle and in the older calves than in the younger ones. BCV-specific IgG was detected in all cattle during the experimental period of up to 22 months. In conclusion, WD was reproduced in seronegative lactating cows. The cows showed a more severe general diseases than seronegative calves infected concurrently. Very long-lasting IgA antibody responses were detected both systemically and locally.

Bovine leukemia virus: early reflections in blood after an experimental infection of calves.

In order to study early alterations in the blood following infection with bovine leukemia virus (BLV) in the natural host, 15 calves were inoculated with blood from a BLV-positive donor cow. The humoral immunological response was followed by ELISA for 2 months. Seroconversion to BLV was demonstrated at 4-5 weeks post-infection. Total and differential leukocyte counts were performed. Acute lymphocytosis was observed at the time of seroconversion in the majority of the experimental calves. By the aid of monoclonal antibodies (mAbs), the proportion as well as the total number of lymphoid cells were studied in four of the calves, applying analytical flow cytometry. At the time of seroconversion the percentage of B-cells increased from 19.1 +/- 7.5% to 37.9 +/- 15.8%, and the T-cells (CD2+) decreased from 36.7 +/- 7.3% to 22.7 +/- 6.0%, the latter being attributable to decreases in the percentage of CD4+ as well as CD8+ T-cells for the infected calves together. Subsequently, altered B/T ratios were observed. In one of the calves an increase in the absolute number of CD5+ cells coincided with an increase in total B-cells. The early phenotypic alterations in lymphocyte subsets, before and after seroconversion to BLV, were comparable to those of non-lymphocytotic and persistent lymphocytotic cattle, respectively. Sera from 15 calves were tested for the presence of interferon (IFN), as measured by antiviral activity. BLV does not appear to induce the production of IFN.

Actinobacillus pleuropneumonia serotype 2--effects on the interferon-alpha production of porcine leukocytes in vivo and in vitro.

Effects of a bacterial infection on the IFN-alpha production in vivo and in vitro were studied in eight specific pathogen free pigs experimentally infected with Actinobacillus pleuropneumoniae. Clinically, the experimental infection was manifested as a febrile stage which lasted approximately one week and by signs of respiratory disease. The Aujeszky's disease virus (ADV) induced IFN-alpha production, assessed in whole blood cultures, was increased for the infected pigs during the febrile stage. Potentiating effects on the IFN-alpha production could be transferred to cultures of purified peripheral blood mononuclear cells with sera collected from the infected pigs during this period of time. Although the experimental infection with A. pleuropneumoniae did not induce any detectable amounts of IFN-alpha in serum or nasal secretion, both a phenol-extract and a heat-inactivated preparation of the bacteria induced low levels of IFN-alpha in cultures of purified PBMC. The interferogenic structures of the bacteria were not identified but there were indications that the bacteria induced IFN-alpha production in the same cell type as ADV.

Influence of experimentally induced endogenous production of cortisol on the immune capacity in swine.

Field studies have suggested that 'stressors', such as transportation and mixing, might interfere with the immune competence of pigs. Therefore, an experimental model was established to study the influence of elevated concentrations of circulating cortisol on the immune capacity in swine. Three experimental groups, with six pigs in each, were immunized twice, 4 weeks apart, with Mycoplasma hyopneumoniae antigen. Endogenous production of cortisol was induced by intramuscular injection of adrenocorticotropic hormone (ACTH) twice daily. One group received ACTH during the week before and after the second immunization, one group during the week after the second immunization only, while one group served as untreated controls. The treatment with ACTH induced high, but physiological, concentrations of cortisol in plasma. Simultaneously, the number of lymphocytes per milliliter blood decreased while the neutrophil number increased. The elevated concentrations of cortisol also coincided with reduced proliferation and interleukin-2 production by blood lymphocytes stimulated with the mitogens concanavalin A and phytohemagglutinin in vitro, while the responses to pokeweed mitogen were less affected. The suppression of mitogen responses was more pronounced in cultures of whole blood than in cultures of purified peripheral blood mononuclear cells (PBMC). Antibody production, induced by M. hyopneumoniae in cultures of purified PBMC was also inhibited by ACTH treatment. Both the rate of increase and the magnitude of the antibody production induced by the primary immunization were reduced. In contrast, no effects of ACTH treatment were recorded for the response to the second immunization or on the serum levels of antibodies to M. hyopneumoniae.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic variation in Con A-induced production of interleukin 2 by porcine peripheral blood mononuclear cells.

Genetic variation in concanavalin A (Con A)-induced proliferation and interleukin 2 (IL-2) production by peripheral blood mononuclear cells (PBMC) was studied in blood collected from 96 piglets, aged 7 weeks. The piglets were the offspring of seven sires and 24 dams. Pronounced differences between litters from various dams were observed in the immune parameters measured. Also, large individual differences in the magnitudes of Con A-induced proliferation and IL-2 production were seen for PBMC collected from individual pigs within each litter. Both the time course and magnitude of IL-2 activity showed genetic variation, as results from the offspring of the seven sires differed significantly. However, only the time course, not the magnitude, of proliferation differed among the offspring groups. It was possible to establish a rank order for the sires based on the IL-2 production of PBMC by their offspring. As IL-2 has a key role in regulating the immune response, mitogen-induced IL-2 activity seems to be a good candidate as a general marker for cell-mediated immunity in pigs.

Detection of B and T cells, with lectins or antibodies, in healthy and bovine leukemia virus-infected cattle.

Lectins, polyclonal antibodies and monoclonal antibodies (MAbs) were evaluated as markers for bovine lymphocytes obtained from healthy animals and from cattle infected with bovine leukemia virus (BLV). In the blood from healthy cattle the proportion of cells identified as T lymphocytes with the lectin Helix pomatia (HP) (67.8 +/- 6.2%) using the indirect immunofluorescence technique was similar to the proportion of cells identified by the MAbs P5 (66.1 +/- 3.8%) and BLT-1 (59.8 +/- 7.1%). The proportion of B cells in blood from healthy animals identified with a polyclonal antibody to bovine IgM (18.0%) was similar to that identified with a MAb to bovine IgM (16.2%). However, greater variation between individual values was detected with the MAb (SD = 8.2) than with the polyclonal antibody (SD = 4.0). In the blood from BLV-infected cattle with persistent lymphocytosis, both the polyclonal and the MAb revealed a threefold increase of B cells. A proportion of the B cells had an increased amount of immunoglobulin molecules in their plasma membrane as indicated by flow cytometry. The proportion of T lymphocytes, identified by the MAb P5, was reduced to one-third of that in non-infected cattle. The indirect HP labelling gave inconsistent results and seems not to detect solely T lymphocytes among blood lymphocytes from BLV-infected cattle.

Tissue chambers--a useful model for in vivo studies of cytokine production in the pig.

An in vivo tissue chamber model was developed to enable studies of local cytokine production and cellular events during inflammatory and immune reactions in the pig. Tissue chambers made of sialistic rubber tubing were surgically implanted in the subcutaneous tissue- and samples of tissue chamber fluid (TCF) and inflammatory cells were collected by aspiration with a syringe. To evaluate the model for local cytokine production, two cytokine inducers, polyribinosinic-polyribocytidylic acid (poly I:C) and fixed Aujeszky's disease virus infected PK15 cells (ADV-PK15), were injected into the tissue chambers and samples of TCF were collected 0, 4, 8, 12, 24 and 48 h post injection. Poly I:C injections induced local production of interferon-alpha (IFN-alpha) as well as tumor necrosis factor (TNF) in the TCF but kinetic differences in the production of the cytokines were noted. Poly I:C also induced an increase in cell numbers in the TCF, mainly due to increased neutrophil numbers. Injections of ADV-PK15 induced local IFN-alpha production in the TCF as long as the pigs were serologically negative to ADV. Immunofluorescence and in situ hybridization techniques could be applied for characterization of TCF cells. Moreover, cells recovered from the tissue chambers were viable and could be used in functional in vitro tests. Taken together, this tissue chamber model could prove very useful in in vivo studies of inflammatory/immune responses and cytokine production in the pig.