Light-chain diversification during pre-B cell differentiation.

The possibility that a committed normal pre-B cell can generate progeny expressing more than one light chain was studied by isoelectric focusing of supernatants from pre-B cells cultured at limiting dilution. Supernatants from mitogen-stimulated mature spleen B-cells analysed on day 6 have shown the presence of a rather homogeneous IgM spectrotype profile. Supernatants from the 8-10-day cultures were usually negative. Isoelectric focusing profiles of supernatants from cultures of bone marrow pre-B cells were different from those of mature spleen cells. Many IgM spectrotypes appeared in the culture supernatants of bone marrow pre-B cells between days 6 and 13, whether the cultures were negative or restricted in their IgM profiles on day 6. These results support the idea that normal pre-B cells, during differentiation, can associate a variety of light chains with an already chosen mu heavy chain.

Effect of toxic shock syndrome toxin-1 on human hemostatic parameters.

The effect of toxic-shock-syndrome-toxin-1 (TSST-1) on coagulation and platelet aggregation was studied in blood samples from human healthy volunteers. TSST-1 at 5 micrograms/ml does not modify the extrinsic or intrinsic coagulation pathways. However, thrombin clotting time (TCT) was significantly increased in the presence of TSST-1. Platelet aggregation was not directly affected by TSST-1 but the toxin strongly inhibited platelet aggregation induced either by epinephrine, adenosine diphosphate (ADP) or platelet activating factor (PAF), while having no effect on aggregation induced by thrombin, collagen or a calcium ionophore. The above results suggest that TSST-1 may bind to a transducer common for some aggregators or that it may induce some non-specific modification of platelet membrane.

Production and characterization of anti-peptide monoclonal antibodies with specificity for staphylococcal enterotoxins A and B.

A synthetic peptide containing selected epitopes from staphylococcal enterotoxin A (SEA) and enterotoxin B (SEB) was used to produce monoclonal antibodies (Mabs) to respective enterotoxins in a single fusion procedure. The peptide inhibited the reaction of polyclonal anti-SEA or anti-SEB antisera with their homologous enterotoxin, thus showing that the chosen epitopes are part of the antibody-inducing enterotoxin sequences. Two Mabs, Mab-A and Mab-B, reacted with both the peptide and with either SEA or SEB. Used in a double antibody sandwich ELISA, the Mabs were able to quantitate the native SEA or SEB toxins at nanogram levels.

Intestinal immune response induced in mice by staphylococcal enterotoxin B.

To investigate the induction of intestinal immunity to staphylococcal enterotoxins (SE) we have chosen the mouse as an experimental model. Since this species is devoid of emetic mechanism, SE can be administered orally without any loss. Mice were treated orally and/or parenterally with staphylococcal enterotoxin B (SEB). The anti-SEB response, either in serum or in the supernatant of in vitro cultured intestinal fragments was determined by enzyme immunoassay (EIA). The results showed that orally given SEB induced specific antibodies both in serum and intestinal secretions. Compared to oral route alone, parenteral followed by oral administration of SEB induced a higher intestinal response with IgA as predominant isotype. Although these results cannot directly be extrapolated to humans or animals with emetic reaction to SE, they do show the implication of intestinal immune system in response to this group of toxins.

Preferential transport into colostrum of Fc fragment derived from serum IgG1 immunoglobulin in the goat.

The selective transport of blood IgG1 into colostrum in ruminant species is not well understood. Therefore, the transport of Fc fragments isolated from serum IgG1 (Fc gamma 1) and IgG2 (Fc gamma 2) in normal and pregnant goats was studied. The animals were injected intravenously with radio-labelled 125I-Fcgamma1 and 131I-Fcgamma2 fragments. The plasma disappearance rate of both fragments showed that at parturition the Fcgamma1 fragment had a higher disappearance rate than Fcgamma2. Over 70 per cent of the inoculated dose of 125I-Fcgamma1 and only 11-12 per cent of 131I-Fcgamma2 could be recovered in the 24 h colostrum. The results indicated that structural differences between the H chains of IgG1 and IgG2 were implicated in the selective transport of IgG1 into colostrum in ruminants.

[Immunochemical and biological properties of goat immunoglobulin G]. / Propriètès immunochimiques et biologiques des immunoglobulines G de la chèvre

Two subclasses of immunoglobulins G, the IgG1 and the IgG2, were isolated from goat serum and colostrum. The two subclasses are different in their physico-chemical and biological properties, but generally their properties resemble those of other immunoglobulins in bovidae.

Biological properties of goat immunoglobulins G.

Ther serum concentration of normal adult goat total IgG was established to be 19.97 +/- 1.55 mg/ml, the IgG1 10.92 +/- 0.84 mg/ml and IgG2 9.07 +/- 0.78 mg/ml. No significant variations were found to be associated with the seasons of the year but changes in concentration, especially in serum IgG1 occur ante- and post-partum. In goat colostrum, the IgG concentration is about 2.4-2.8 times greater than in serum and the IgG1 subclass accounts for 95-98 per cent. During the immune response the IgG1 rises sharply whereas variations in IgG2 concentration are less evident. Both IgG subclasses are active in haemagglutination, although the IgG1 is 22-52 times more efficient. As in all ruminants, only IgG1 fixes complement in the classical test. Differences exist between IgG subclasses in their ability to induce PCA reactions. IgG2 subclass is active only in homologous species whereas the IgGl in heterologous species. Cytophilic activity is associated with IgG2 subclass.

A mouse model for staphylococcal enterotoxins toxicity.

The study of staphylococcal enterotoxins (SE), which can adversely affect man and animals, is hindered by the absence of a practical animal model. Only humans and primates are sensitive to SE oral intake whereas other species such as cats and dogs require intravenous SE administration to induce biological effects. Rodents are very resistant even to relatively high doses of SE. Treatment of mice with D-galactosamine (20 mg/mouse) rendered them highly susceptible to micrograms of toxins leading to lethal shock. Differences in toxic potential have been observed between types of SE. Carboximethylated SE, which have been shown not to induce emesis in primates were also able to induce shock. Anti-tumour necrosis factor antiserum (anti-TNF-alpha) and, to a lesser extent anti-SE antisera, reduced the lethality to SE in D-galactosamine-treated mice. This proposed cost-effective animal model may be used to study the immunopathological properties of natural, recombinant or mutant SE.

Superantigens of microbial origin.

Food poisoning associated staphylococcal enterotoxins and other bacterial products of diverse origin are now the focus of immunological research. These substances have special properties which determine their designation as superantigens. They influence T cell functions by controlling their repertoire, their cytokines production and their modulation of the immune response. As a consequence, superantigens might be at the origin of bacterial and autoimmune diseases. In this review we describe mainly the staphylococcal enterotoxins as representative members of the superantigen family.

The role of colorstrum on the occurrence of immunoglobulin G subclasses and antibody production in neonatal goats.

Quantitative determinations of IgG1 and IgG2, in one group of colostrum-fed and one group of colostrum-deprived neonatal goats revealed that the occurrence of the IgG1 subclass preceeded that of the IgG2 in both cases. In the colostrum-fed animals the IgG2 appeared, on an average, in the fourth week of life whereas in the colostrum-deprived animals the IgG2 was detected as early as three weeks after birth. At the age of twelve weeks the mean concentrations for IgG, and IgG2 were higher in the animals deprived of colostrum. The immune response to human gamma globulin was studied in colostrum-fed and colostrum-deprived neonatal goats which were immunized at birth and again after four and eight weeks. Following the first two antigen administrations a significantly higher response was obtained in the colostrum-fed neonates. However, the third injection determined a similar response in both groups. A marked suppressive effect on the immune response was observed in colostrum-fed neonatal goats when specific antibodies were present in the colostrum after preimmunization of the mothers with human gamma globulin.

Prevention of the enhancing effect of mucin and iron in mouse meningococcal infection.

In vivo resistance of mice to Neisseria meningitidis was entirely abrogated by a concomitant administration of mucin and iron with N. meningitidis organisms. Resistance, however, was restored when the latter challenge was given to animals which had been immunized 7 days previously with a crude extract of meningococcal antigens (MA), BCG, or proteose peptone. These results suggest that depression or activation of the reticuloendothelial system (RES) may be important in resistant of mice to meningococcal infection. Also, like BCG, MA inoculation was able to prevent infection by Listeria monocytogenes indicating its marked ability to activate the RES. The data show that immunization can induce nonspecific RES stimulation and that the nonspecific resistance persists for at least 7 days.

Modulation of the immune response by passive antibodies. IV. Effects of IgG1 and IgG2 anti-hapten antibodies.

The effects of IgG1 and IgG2 anti-hapten antibodies waere studied on celluar and humoral reactions induced by immunization with a hapten-carrier complex. IgG2 was shown to depress delayed hypersensitivity reactions to the carrier and to enhance anaphylactic reactions to both the hapten and the carrier whereas IgG1 appeared to have no activity except a little enhancing effect on antibody synthesis to the carrier. The regulatory role of IgG2 antibodies, which were cytophilic for macrophages, in the immune response to a hapten-carrier conjugate is discussed.

Evaluation of the immunogenicity of a CaCl2 extract from Neisseria meningitidis group Y.

Cross-protection has already been demonstrated in mice after vaccination with a CaCl2 extract from the Neisseria meningitidis group Y Slaterus strain. The immunogenicity of such extracts from group Y cells, cultivated in a fermenter in Neisseria chemically defined medium, against virulent groups A, B, and C meningococci has been evaluated by two different animal models and a microbactericidal procedure. The mouse challenge system has revealed that the active cross-production observed 7 days after a single immunization with the extract was probably nonspecific, since bacillus Calmette-Guérin gave similar results. However, after three vaccinations, active cross-protection was observed, mainly against the strains of groups B and C, for at least 35 days after the last injection. In the mouse bacteremia model, the extract had a protective effect mainly against the homologous group Y strain but in a few experiments a significant protection was also obtained against the strains of groups A and B. The microbactericidal test revealed that even after three injections of mice, guinea pigs, or humans with the extract only the homologous bactericidal activity was induced. Since there was no close correlation between the results obtained with the two animal models and also with the microbactericidal procedure, no definitive conclusion can be drawn on the protective potential of our extract.

Production of human and murine interleukin-2 by toxic shock syndrome toxin-1.

Toxic shock syndrome toxin-1 (TSST-1), isolated from Staphylococcus aureus strains associated with toxic shock syndrome (TSS), is known as a potent mitogen and interleukin-1 inducer. The potential of TSST-1 as an interleukin-2 (IL-2) inducer was tested on human peripheral blood lymphocytes (HPBL) and murine spleen lymphocytes (MSL). These cells were incubated with TSST-1 and the supernatants analysed for IL-2 production. Preincubation of IL-2-dependent indicator cells (IC) with a monoclonal antibody specific for murine IL-2 receptors inhibited their proliferation by supernatants of TSST-1-treated MSL, thus strongly suggesting that they contain IL-2. The concentrations of TSST-1 required for HPBL or MSL to produce IL-2 ranged between 10(-1) and 10(-4) micrograms/ml. The amount of IL-2 units/ml varied little from one experiment to another. In contrast, IL-2 production by PHA-stimulated HPBL or Con A-stimulated MSL showed great variability and dependence on mitogen concentration. T-cell depleted MSL exposed to TSST-1 produced less IL-2. Experiments with germ-free mice and TSST-1-primed mice demonstrated that IL-2 production is not related to TSST-1 antigenicity.

Stimulation of T cells and induction of interferon by toxic shock syndrome toxin 1.

Toxic shock syndrome toxin 1 (TSST-1) is a potent immunomodulating substance isolated from Staphylococcus aureus strains associated with toxic shock syndrome (TSS). Flow cytometric analysis was used to compare scatter changes in several cell-surface phenotype markers on human mononuclear cells exposed in vitro to TSST-1 or to phytohemagglutinin, a lectin with similar effects on the immune response. The results showed differences between PHA and TSST-1 in the appearance of the tested T cell subset markers and of interleukin 2 receptors. In general, the stimulation of mononuclear cells by TSST-1 was slower than that by phytohemagglutinin. TSST-1 induced the production of interferon in cultures of murine spleen cells. By means of inhibition studies with specific antibodies to interferon, the interferon produced was characterized as the gamma type. Human mononuclear cells exposed to the toxin also produced gamma interferon, with levels similar to those induced by staphylococcal enterotoxin A, a known potent interferon inducer. The induction of gamma interferon by TSST-1 may play a role in the immunosuppression caused by TSST-1.

Menningococcal antigens (MA): a novel immune stimulant in experimental neoplasia.

An extract of the meningococcus antigens (MA) prepared from N. meningitidis was tested for an anti-tumor effect in rat and murine metastasizing tumor models. Effectiveness of MA in each model varied with dose and was manifested as significantly improved survival of the treated animals. Growth of the primary Fischer bladder carcinoma (FBCa) and metastases to lungs and lymph nodes were significantly inhibited in F344 rats treated weekly with 1 mg MA. Administration of MA at 100 micrograms per animal significantly prolonged survival of P815 mastocytoma-inoculated DBA/2 mice. Survival of C-26 colon adenocarcinoma-bearing Balb/c mice was significantly improved in animals that received weekly injections of 20 micrograms MA, without significant effect on the development of local tumor. The meningococcal antigens demonstrate strong mitogenic activity in B-cell-enriched murine spleen cultures. Thus the immunostimulatory activity of MA in experimental malignancy could involve, directly or indirectly, activation of B lymphocytes.

Mouse immune response to meningococcal antigens.

The mouse immune response against Neisseria meningitidis was studied by using an extract from group Y (Slaterus) known to contain protein antigens common to other meningococci. By using a solid-phase radioimmunoassay, high titers of specific IgM and IgG class antibodies were measured which lasted over 2 months after immunization. These antibodies cross-reacted with similar extracts from other meningococci groups. Bactericidal antibodies directed against protein antigens were also elicited after immunization and they belonged to IgM, IgG2a, and IgG2b isotypes. Cellular immunity, expressed as delayed type hypersensitivity under the conditions tested, could be detected neither in homologous nor heterologous reactions.