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D Primi

Publications and source records attributed to D Primi.

At least 91 records · Page 5Linked to original sources
PubMed1982

Monoclonal antibodies coupled to LPS specifically induce synthesis of immunoglobulins with complementary variable region determinants.

The aim of this work was to investigate whether LPS coupled to monoclonal immunoglobulins would, at certain critical doses, specifically trigger B cells carrying immunoglobulins with V region complementary to that of the immunogen. Thus sera of BALB/c mice injected with 5 micrograms of LPS-M-460 contained immunoglobulins that specifically reacted with the M-460 protein. Similarly, injection of LPS coupled to a monoclonal anti-M-460 immunoglobulin F6(51) resulted in the selective production of antibodies specific for F6(51). In addition, radioimmunoassay studies clearly showed that the induced immunoglobulins reacted with F6(51) through idiotypic interactions. This immune response is independent from T cells because nu/nu responded as well as their heterologous littermates. Kinetic studies showed that the titer of F6(51) complementary antibodies in mice injected with F6(51)-LPS remained elevated for more than 1 mo, and that the majority of these immunoglobulins belong to the IgM class. Surprisingly, F6(51)-LPS induced F6(51)-specific antibodies only in mice with the Igh-a allotypic haplotype, indicating that although thymus-independent, the response is under regulation. Finally, addition of small amounts of F6(51)-LPS to cultures of B cells from BALB/c mice resulted in the secretion of antibodies capable of reacting with F6(51). These low concentrations failed to activate nonspecific cells. Consequently our data offer the possibility of selectively inducing in vivo or in vitro idiotype-positive immune responses in the complete absence of the antigen recognized by the induced immunoglobulins.

Animals↗
PubMed1981

Induction and regulation of silent idiotype clones.

In order to study whether allotype linkage of idiotype expression is related to the total absence of structural gene(s) or to regulatory mechanisms acting on its phenotype expression, the M460 clone expression was followed in b cells from various inbred and recombinant strains of mice cultured at low density in the presence of lipopolysaccharide. Under these conditions, all cultures were found to contain anti-trinitrophenyl (TNP) antibody plaque-forming cells, some of which inhibitable by anti-M460 immunoglobulins. In the course of these studies, it also became apparent that, even in the absence of T cells, B lymphocytes are able to exert regulatory functions. Experiments carried out using anti-M460 hybrid cells F6(%!), and affinity-purified anti-(anti-M460) antibodies revealed that clonotype regulation by B cells is mediated by idiotype-auto-antiidiotype interactions.

Animals↗
PubMed1981

Recognition of MOPC-460 variable region determinants by polyclonally distributed triggering receptors on B lymphocytes.

Purified M460 protein-induced untreated and anti-Thy 1.2 and complement-treated murine spleen cells to proliferate and differentiate in vitro. Fc receptor complexing was not responsible for the phenomenon, since M460 Fab fragments retained the B cell triggering activity. Activation was inhibitable by the addition of DNP-glycine to cultures and could also be detected by using spleen cells from various strains of mice, including the C3H/HeJ, which is genetically nonresponding to LPS. Hybrid molecules were constructed between the M460 proteins and the products of 2 myelomas that do not activate B cells, namely, X25 and X24. The only hybrid molecules that retained triggering activity were (L460-Hx25)2. Interestingly, the same molecule was also the only one recognized by an anti-M460 monoclonal antibody (F6(51)) that has been previously shown to induce B cells to proliferate and differentiate. The data suggest the existence on B lymphocytes of a network of polyclonally distributed mitogen receptors that share determinants cross-reacting with immunoglobulin idiotypes.

Animals↗
PubMed1980

The role of immunoglobulin receptors and T cell mediators in B lymphocyte activation. I. B cell activation by anti-immunoglobulin and anti-idiotype reagents.

The possibility that the failure of anti-mouse immunoglobulin (Ig) antibody to induce antibody synthesis by B cells might be due to reversible receptor blockade was investigated. Murine spleen cells were cultured for 3 days in the presence of minute quantities of intact of (Fab') fragments of rabbit anti-mouse Ig antibody. Thereafter, the cells were washed and either trypsin treated or not before reculturing for 18 hr. Only cells that had been trypsinized after culturing with either intact or fragments of anti-Ig gave a vigorous polyclonal antibody response. This response was extremely T dependent, since T cells or culture supernatants from Con A-activated T cells were required for the B cell response. Moreover, anti-delta was much more effective than anti-mu in inducing antibody synthesis. Finally, the use of three different anti-idiotypic antisera rather than anti-Ig reagents selectively activated the specific idiotype in each instance. The findings demonstrate that anti-Ig reagents can potentiate the response of B cells to signals delivered by T cells.

Animals↗
PubMed1979

A hemolytic plaque assay for activated murine T cells.

In an earlier report, it was shown that murine spleen cells cultured with concanavalin A (Con A) released into the culture supernatants helper and suppressor substances for antibody production. The present communication describes the production of rabbit antisera against culture supernates from Con A-activated spleen cells and their use in a plaque assay for mitogen-activated T cells. The plaque assay, utilizing SRBC to which Staphylococcal protein A had been coupled, the developing anti-supernatant antiserum and guinea pig complement, readily detected secreting T cells. The T-cell nature of the plaque-forming cells (PFC) was established principally by the following: (a) the majority of lymphocytes in the centers of plaques were Thy-1-positive by fluroescence; (b) spleen cells depleted of B cells by incubation in plastic dishes coated with rabbit anti-mouse Ig antibody gave greatly enriched PFC responses; (c) anti-Thy-1 and anti-Lyt-2.2 treatment of spleen cells almost completely depleted PFC; (d) T-cell mitogens (Con A and phytohemagglutinin) but not B-cell mitogens (lipopolysaccharides) induced PFC responses; (e) T cells maintained in culture for 10 d with Con A and T-cell growth factor yielded PFC. Kinetic and dose response studies showed that high doses of mitogen induced rapidly appearing T-PFC and the responses peaked at day 1--2 of culture. Lower doses of mitogen-induced PFC required longer periods of incubation for detection, indicating that cell activation and secretion may be different dose-dependent activities of mitogens. Another noteworthy finding was that the antiserum reacted with surface antigens of T-PFC, indicating that secreted products are expressed on the membranes of T cells, offering the possibility of isolating populations of cells with specific secretory potential. Although the precise nature of the T-cell products detected by the antiserum used in this assay are unresolved, 10% of the target-cell-adherent population from spleen cells of BALB/c mice sensitized to L929 cells formed plaques. This suggests that the antiserum has significant activity against the products of cytotoxic T cells, a finding which accords with the activity of anti-Lyt-2.2 serum against mitogen-induced T-PFC. The method clearly offers new possibilities for the analysis of T cells and their products and should provide an important approach to the clonal analysis of lymphokine production.

Animals↗
PubMed1979

Rosette formation between murine lymphocytes and erythrocytes. A new locus in the H-2 region.

More than 5% of murine splenic lymphocytes form rosettes with syngeneic erythrocytes. This property was maximally expressed when the lymphocytes were cultured for 24 h before rosetting. About 70% of the rosetting lymphocytes were B cells and 30% were T cells on the basis of surface immunoglobulin and the Thy-1-antigen. Capping surface immunoglobulin had no effect on the capacity of lymphocytes to form rosettes, indicating that the receptor in question was not immunoglobulin. The capacity of lymphocytes to form rosettes with erythrocytes from other strains of mice was H-2 restricted. Extensive pairings of congenic and recombinant strains as donors of lymphocytes and erythrocytes showed that none of the known loci within the H-2 region-controlled rosetting. The involvement of regions on chromosome 17, telomeric or centromeric to H-2, was also excluded. The data were only compatible with the conclusion that this form of self-recognition is associated with a new locus (or loci) mapping between H-2G and H-2D.

Animals↗
PubMed1979

Con-A-activated T cells secrete factors with polyclonal B-cell-activating properties.

Concanavalin A induced polyclonal antibody synthesis in normal spleen cells in vitro. Optimal responses were obtained by Con A concentrations lower than those optimal for induction of DNA synthesis. T cells, but not macrophages, were necessary for the effect. Spleen cells from nude mice were not activated, whereas cells from the LPS non-responder stain C3H/HeJ were activated to polyclonal antibody synthesis by Con A. Supernatants from Con A activated spleen cells could by themselves induce polyclonal antibody synthesis in untreated spleen cell cultures, even when Con A had been removed by absorption with Sephadex G-50 and when alpha-methyl-mannoside was present in the secondary cultures. T cells produced the active supernatants, which were competent to induce polyclonal antibody synthesis, but not DNA synthesis, in both H-2-incompatible and compatible strains. When the supernants were absorbed with erythrocyte antigens, they specifically induced an enhanced response, in secondary cultures, to the antigen used for absorption. Possible mechanisms of this specific effect are discussed.

Animals↗
PubMed1978

Role of suppressor T cells in autoimmune responses induced by polyclonal B cell activators.

In order to investigate a possible role of suppressor T cells in the maintenance of self tolerance, we compared the autoimmune response induced by LPS in cultures of untreated spleen cells with the one of anti-theta treated spleen lymphocytes. It was constantly found that T cell depletion never resulted in an increase in the number of plaques directed against autologous albumin coupled SRBC. The same finding was also apparent when the autoimmune response given by spleen cells of old, normal or thymectomized and young untreated animals was compared. In order to exclude the possibility that lack of increase of the autoimmune response in animals with T cells deficiency was due to long-lived suppressor functions, cells or factors, we compared the response to autologous albumin, as induced by LPS, in spleen cells of nude mice with the one given by their normal littermates. Since even in this instance no significant increase could be detected, we conclude that suppressor cells do not play an active role in the maintenance of self tolerance.

Animals↗
PubMed1978

Genetic control of lymphocyte suppression. I. Lack of suppression in aged NZB mice is due to a B cell defect.

Con A-activated cells from old NZB mice were found capable of inhibiting the polyclonal response of cells from young NZB and BALB/c animals. Furthermore, Con A-preactivated spleen cells from young NZB and BALB/c mice did not significantly affect the response of spleen cells from old NZB mice. These results suggest that the defective suppressive activity in old NZB mice may be traced to a defect at the B cell level.

Aging↗
PubMed1977

Characterization of self-reactive B cells by polyclonal B-cell activators.

The existence of autoreactive B cells was predicted by theoretical considerations and, recently, confirmed by direct experiments. The aim of the present work was to investigate if the capacity of self-reactive B cells to be activated with different polyclonal B-cell activators (PBA) reflects the heterogeneity of the response as seen in all the Ig-positive cells. We injected mice with dextran sulfate, lipopolysaccharide from Escherichia coli 055:B5, and purified protein derivate of turbercle bacteria RT32 and studied the complement-dependent cytotoxicity against syngeneic spleen cells caused by the sera from injected mice with regard to the different parameters used for characterization of B-cell subpopulations. It was found that the capacity of self-reactive B cells to secrete antibodies reflects the polyclonal-activating capacity of the PBA used. The implications of these findings for the understanding of the triggering mechanism of B lymphocytes and for self-nonself discrimination are discussed.

Animals↗