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G J Nossal

Publications and source records attributed to G J Nossal.

At least 163 records · Page 9Linked to original sources
PubMed1978

B lymphocyte subpopulations separated by velocity sedimentation. II. Characterization of tolerance susceptibility.

Neonatal and adult splenic B lymphocyte subpopulations, separated by velocity sedimentation, were tested in an in vitro splenic focus assay for their susceptibility to tolerance induction with hapten-protein conjugates. At least two tolerizable B cell subsets have been defined in the neonatal spleen; one comprising the slowly sedimenting, small lymphocytes and the other comprising the very rapidly sedimenting, large lymphocytes. In addition, a rapidly sedimenting large B cell subset in the adult spleen was found to be highly susceptible to tolerance induction. It was suggested that the inability to detect this susceptibility in unfractionated adult spleen was due to the low proportion of these very large lymphocytes in the total spleen cell population. The tolerizable B cell subsets presently defined probably represent the least mature B lymphocytes detectable in the splenic focus assay.

Aging↗
PubMed1977

Role of IgD in the immune response and tolerance. I. Anti-delta pretreatment facilitates tolerance induction in adult B cells in vitro.

Adult spleen cells from C57BL.Ige mice, which generally are resistant to in vitro tolerance induction in the B-cell compartment, became hyporesponsive (tolerant) when cultured with antigen in the presence of an anti-allotype serum. Both antigen and anti-delta had to be present for this effect, which was hapten-specific and did not occur in C57BL/L mice, which lack the Ig5-1 allotype of the delta-chain detected in this system. Preculture with anti-mu serum plus antigen, in contrast, did not cause tolerance induction in adult spleen B cells of either strain. These results suggest that the surface IgD may act as a failsafe receptor to prevent tolerance induction in adult B cells. Tolerance studies with spleen cells from mice with markedly reduced numbers of IgD+ve cells, because of regimen of repeated injections of anti-delta serum beginning at birth (delta-suppressed mice), confirmed the importance of membrane IgD in preventing tolerance, because such delta-suppressed mice were hypersusceptible to tolerance by antigen alone. Inasmuch as immature B cells lack IgD on their surface, these studies suggest that acquisition of IgD is an important maturational step in the ability of murine B cells to discriminate tolerogenic and immunogenic signals.

Animals↗
PubMed1976

Requirement for persistent extracellular antigen in cultures of antigen-binding B lymphocytes.

A system was established to assess the requirement for continuous presence of antigen in B-lymphocyte activation to antibody formation. Mouse spleen B lymphocytes, enriched for cells bearing anti-NIP (hapten 4-hydroxy-3-iodo-5-nitrophenylacetic acid) receptors, were pretreated briefly with NIP-POL (polymerized flagellin) antigen, washed, and added in small numbers to microcultures. The behaviour of these cells was compared with that of cells cultured in the continuous presence of antigen. Unfractionated spleen cells were studied under similar conditions. In contrast to unfractionated cells, enriched cells could not be triggered effectively by brief contact with antigen at any concentration tested. Fewer cells were activated, and clone size was smaller after brief contact with antigen than when antigen was present continuously. Furthermore, brief contact at high concentration did not cause tolerance induction.

Animals↗
PubMed1976

Antigen-induced aggregation and modulation of receptors on hapten-specific B lymphocytes.

Mouse spleen cells were subjected to a fractionation procedure designed to enrich for 4-hydroxy-3-iodo-5-nitro-phenylacetyl (NIP)- or DNP-specific B lymphocytes, which depended on adherence of specific cells to a layer of hapten-gelatin at 4 degrees C, recovery of bound cells by melting, and digestion of adherent antigen by collagenase. A population of cells resulted which contained 90% typical B cells and 37% of cells capable of binding a fluorescent, haptenated polymeric protein. Fractionated cells were reacted in vitro with fluorescent conjugates of the specific haptens with polymerized flagellin [NIP-polymerized flagellin (POL)-tetramethylrhodamine isothiocyanate conjugate or DNP-POL-fluorescein isothiocyanate conjugate] under a variety of conditions, with the aim of investigating the behavior of Ig receptors on B lymphocytes after exposure to antigen; Experiments were performed with immunogenic and tolerogenic concentrations of antigen. Furthermore, four experimental designs were used, namely: (a) brief labeling with fluorescent antigen followed by culture without antigen (pulse design); (b) culture in the continuous presence of fluorescent antigen (continuous-labeling design); (c) culture in the continuous presence of nonlabeled antigen followed by labeling of unoccupied receptors by fluorescent antigen (receptor status design); and (d) culture with nonlabeled antigen for 2 h followed by incubation without further antigen for 20 h and labeling with fluorescent antigen (modulation design). Further insight into receptor occupancy and distribution was gained by the use of fluorescent antihapten and antiglobulin reagents. It was found that both immunogenic and tolerogenic antigen concentrations caused rapid patching and capping of the receptors to which they attached, followed by endocytosis and probably some shedding of Ig receptors. However, a proportion of cells continued to bear some cell surface antigen for 24 h. The immunogenic antigen concentration failed to completely remove the receptor coat from the cell surface. At all stages of immunogenesis, plentiful unoccupied receptors could be demonstrated. The tolerogenic concentration nearly saturated available receptors, and in its continuous presence, only few unoccupied or antigen-occupied surface receptors could be detected after 24 h of culture. Experiments of the modulation design showed that brief incubation with the tolerogenic concentration appeared to suppress receptor resynthesis, as few new receptors could be demonstrated after 20 h of further culture without antigen. Experiments were performed to determine whether fractionated cells prepared from spleens of 8-day-old mice showed an unusual tendency for modulation, even with immunogenic antigen concentrations. They were found to behave essentially like adult fractionated cells. The results are discussed in the framework of current theories of B-lymphocyte activation and tolerization.

Animals↗
PubMed1976

Single cell studies on the antibody-forming potential of fractionated, hapten-specific B lymphocytes.

This study addresses itself to the problem of antibody formation in vitro by mouse splenic B lymphocytes enriched for reactivity to the hapten NIP by the hapten-gelatine binding and melting technique of Haas and Layton (1975). Small numbers of NIP-gelatine-bound B cells were placed in microcultures either by bulk dispensing of dilute cell suspensions, or by micromanipulation under direct microscopic visualization. Antibody formation was induced by the T cell-independent hapten-protein conjugate NIP-polymierized flagellin, using 10(4) thymus cells per microlitre as 'filler' cells. The frequency of precursors of NIP-specific antibody-forming cells among bound cells was about 2-2 X 10(-2) (one cell in forty-five) by both statistical and direct evaluation, after adjustment for a background frequency of 6-10 X 10(-8) precursors in the thymus filler cells. Single clones commenced antibody secretion asynchronously, as shown by the fact that the incidence of positive cultures continued to rise over the whole three days of culture, and that very small clones of one to four plaque-forming cells (PFC) were still found on day 3. The mean PFC number per positive culture rose from 1-2 at day 1 to 4-7 at day 2 and about 20 at day 3.

Animals↗
PubMed1975

Growth of B-lymphocyte colonies in vitro.

In semisolid agar cultures containing mercaptoethanol, cells from the spleen, lymph nodes, marrow, peritoneal cavity, thoracic duct, and blood of normal mice generated clusters and colonies of up to 3,000 cells. Colony numbers and growth were markedly enhanced by the addition of sheep red cells. The frequency of colony-forming cells in the spleen or lymph nodes was 0.5-2.0%, and cluster forming cells were approximately five times more numerous. The mononuclear cells comprising these colonies had the electronmicroscopic morphology of immature lymphoid and plasma cells. The majority of the cells possessed Fc receptors, 61-69% reacted with anti-mu-serum and 4-11% with anti-gamma2-serum. Analysis of single cells from individual colonies indicated a higher frequency of the cells with membrane immunoglobulin and a clonal pattern of anti-mu or anti-gamma-reactivity. The clonal nature of colonies was supported by an analysis of NIP-binding cells in colonies grown from CBA spleen cells enriched for NIP-binding cells. Mass-harvested colony cells synthesized immunoglobulin in short-term liquid cultures. It is concluded that the colonies are clones of functionally active B-lymphoid cells.

Animals↗
PubMed1975

Evidence for the clonal abortion theory of B-lymphocyte tolerance.

This paper deals with the behavior of adult mouse bone marrow cells placed in tissue culture with or without antigen, and subsequently assessed for immune competence after adoptive transfer into lethally X-irradiated, syngeneic hosts. Attention was focussed on B lymphocytes through using hapten human gamma globulin (HGG) preparations as putative tolerogens in tissue culture, the T-cell-independent antigens DNP-POL and NIP-POL as challenge injections in adoptive hosts, and numbers of hapten-specific PFC in host spleens for the quantitation of immune competence. It was found that the capacity of bone marrow cells to mount an adoptive immune response rose by a factor of about fivefold over 3 days in tissue culture. This rise was completely abolished by the presence in the culture of hapten-HGG conjugates with about one mole of hapten per carrier molecule. The prevention of the emergence of immune competence amongst maturing B cells was termed clonal abortion tolerogenesis. Dose-response studies showed the lowest effective antigen concentration to be between 2.5 times 10- minus 10 and 2.5 times 10- minus 9 M, and a standard concentration of 2.5 times 10- minus 8 M was chosen as producing near maximal effects. The tolerance was antigen-specific and time-dependent, being maximal only when antigen was present continuously as the cultured cells was maturing. It did not depend on the presence of T lymphocytes in marrow, and was not of an "infectious" type. In contrast to tolerogenesis of mature B lymphocytes by high antigen concentrations, it could not be abolished by lipopolysaccharide. We speculate that clonal abortion may be a tolerance mechanism of great physiological significance for self-recognition, and discuss the results in the framework of other recent tolerance models, including those involving receptor blockade and suppressor T cells.

Animals↗
PubMed1975

Kinetics of antibody formation and regulatory aspects of immunity.

This paper, which is to be read in conjunction with that of Dr. J.F.A.P. Miller earlier in this volume, addresses itself to the kinetics of antibody production and to the regulation of the immune response. It is divided into four main sections. The first examines the kinetics of antibody production to a single, strong challenge injection of antigen. The cellular events involved in the latent period and the subsequent exponential phase of antibody production are examined from the viewpoint of four key concepts: triggering, clonal expansion, IgM to IgG switch and affinity maturation. The second section examines the major regulatory influences and feedback loops in immunity. Antigen is discussed as an agent capable of causing tolerance as well as triggering. Antibody is considered an important regulator, and the mechanisms of IgM-positive feedback, IgG-negative feedback, and tolerance and blockade effects of immune complexes are outlined. Immunological memory, the opposite phenomenon to tolerance, is briefly described, as is the importance of genetic factors. The third sections looks at more complex models of the immune response, and in particular at the lessons to be learnt from tumour progression.

Animals↗