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B Subbarao

Publications and source records attributed to B Subbarao.

29 records · Page 2Linked to original sources
PubMed1987

Early events in B-cell activation: anti-Lyb2, but not BSF-1, induces a phosphatidylinositol response in murine B cells.

Previous studies have indicated that the murine surface antigen Lyb2 is involved in an activation pathway that apparently does not involve the surface immunoglobulin receptor. As sIg has been shown to transduce its activation signal through the breakdown of phosphatidylinositol (PI), and since activation via Lyb2 does not involve sIg, it was of interest to determine if binding to Lyb2 generates a PI response. We have demonstrated that an allele-specific monoclonal antibody to Lyb2 (anti-Lyb2 mab), which has previously been shown to drive B cells into S, also activated PI metabolism in these cells. This activation occurred in a dose-dependent and allele-specific manner. Antibodies to other B-cell surface molecules such as Ia did not induce a PI response. The effect of anti-Lyb2 mab was always less in magnitude than that induced by anti-IgM, but the effects of the two antibody preparations were most comparable in larger, presumptively preactivated cells. To explore the issue that Lyb2 may represent a receptor for a growth factor, possibly the early-acting B-cell growth factor BSF-1, we studied the PI response to BSF-1 and the effect of BSF-1 on Lyb2-induced PI turnover. BSF-1 neither induced a PI response nor inhibited competitively the response induced by anti-Lyb2 mab.

Alleles↗
PubMed1986

Enhancement by monoclonal anti-Lyb-2 antibody of antigen-specific B lymphocyte expansion stimulated by TNP-Ficoll and T lymphocyte-derived factors.

By using antigen-specific populations of B cells (TNP-ABC) we have demonstrated that the type-2 antigen TNP-Ficoll was capable of initiating B cell proliferation only in the presence of T cell-derived factors. Monoclonal-anti-Lyb-2.1 antibody acted synergistically with a T cell-derived supernatant, as well as with B cell-stimulating factor (BSF-1) to enhance the level of B cell expansion obtained in this in vitro system. This effect of anti-Lyb-2.1 mAB was observed at each day of the antigen-driven B cell expansion and was seen only with B cells purified from strains expressing the Lyb-2.1 allele. The epitope density of hapten on the Ficoll plays a critical role in this process, because Ficoll that is haptenated with low density of hapten was not found to be stimulatory. These results suggest that the Lyb-2 surface molecule influences the antigen-driven B cell growth that is stimulated by type 2 antigens and BSF-1.

Animals↗
PubMed1979

Role of a nonimmunoglobulin cell surface determinant in the activation of B lymphocytes by thymus-independent antigens.

Lyb 5 is a B-cell alloantigen which is expressed on 50-60% of B cells. It was defined originally on the basis of cytotoxicity. We have described a new reactivity within the anti-Lyb 5 serum on the basis of selective inhibition of antibody responses in vitro by this antiserum in the absence of complement. This inhibitory activity of anti-Lyb 5.1 serum appears to be due to recognition of antigenic determinants different from the prototype antigens detected in the cytotoxicity assay. Anti-Lyb 5 serum incorporated into spleen cell cultures selectively inhibits antibody responses to a class of thymus-independent antigens (TI-2) previously characterized by their failure to elicit antibody formation in immature mice or in the defective CBA/N strain. Responses to optimal concentrations of TI-1 antigens, which can induce antibody synthesis in these mice, are unaffected by the addition of anti-Lyb 5.1 serum. The B-cell alloantigen defined by this functional assay is designated tentatively Lyb 7 and it is shown to be distinct from cell surface immunoglobulins. Lyb 7 appears to have a role in the activation of B lymphocytes by the TI-2 class of thymus-independent antigens.

Antibody Formation↗
PubMed1979

Tritium (3H) radiolabeling of protein A and antibody to high specific activity: application to cell surface antigen radioimmunoassays.

Staphylococcal protein A and several different immunoglobulins have been radiolabeled to high specific activities (greater than 10(6) cpm/microgram) by reductive methylation with tritiated (3H) sodium borohydride. The proteins retain excellent functional and antigenic properties. The utility of these reagents in a variety of assays for cell surface antigens is illustrated. The results indicate that this radiolabeling procedure may become the method of choice for many cell surface and solution immunoassays.

Animals↗
PubMed1979

Lyb-7, a new B cell alloantigen controlled by genes linked to the IgCH locus.

Anti-Lyb-5.1 serum contains antibodies against two different B cell surface antigenic determinants, Lyb-5.1 and Lyb-7.1, which are defined in cytotoxicity and functional tests, respectively. The antibody against Lyb-7.1 is identified by its ability to specifically inhibit in vitro primary antibody responses to TNP-Ficoll. Anti-Lyb-5.1 serum can be made monospecific for anti-Lyb-7.1 activity by absorption with spleen cells from AL/N mice which have been typed as Lyb-5.1+, Lyb-7.1-. Lyb-5.1 and Lyb-7.1 are each under control of one or one set of closely linked genes. The loci specifying Lyb-5.1 and Lby-7.1 are not linked to each other nor to M1s and H-2 loci. However, the gene controlling the expression of Lyb-7.1 is linked to the genes coding for the constant region of immunoglobulin heavy chains.

Animals↗
PubMed1978

B lymphocyte development, heterogeneity, and function.

Thymus-independent (B) lymphocytes are a heterogeneous group of cells which, it is increasingly clear, undergo an ordered sequence of differentiation steps from stem cells to antibody producing cells. Through the study of the immunologic potential of B lymphocytes from neonatal mice and from mice with an X-linked immune defect, it has become possible to assign certain functions to cells of distinct differentiated states. Furthermore, a differentiation antigen, Lyb 5, has been identified which acts as a marker of a particular subset of B lymphocytes in normal mice. Initial studies of the functional properties of Lyb 5+ and Lyb 5- B lymphocytes are described.

Animals↗
PubMedDate not supplied

Antibody responses to thymic independent antigens in the peripheral and mesenteric lymph nodes of mice.

Differentiation of B lymphocytes from various peripheral lymph nodes (PLN) of mice was studied in the in vitro and in vivo conditions. Subcutaneous (SC) immunization in the foot pads with thymic independent (TI)-2 antigens such as polyvinyl pyrrolidone (PVP), R36A, and Trinitrophenyl (TNP)-Dextran failed to elicit plaque forming cell (PFC) responses from the draining popliteal and inguinal lymph nodes, whereas the splenic B cells of these animals exhibited good PFC response. Injection of unconjugated Brucella abortus (BA) along with TNP-Dextran was able to induce anti-TNP PFC formation from the draining lymph node B cells. However, PVP + BA or R36A + BA failed to stimulate such antigen specific B cell responses from the lymph nodes. Since TI antigens are metabolized slowly because of their long repeating subunits, we measured antibody responses up to 8 weeks after SC immunization with TNP-Ficoll and failed to observe any anti-TNP IgM PFC in the lymph nodes. TNP-Ficoll, in contrast to TI-1 antigen TNP-BA, did not induce IgG PFC response in the draining lymph node cells. In in vitro cultures, TNP-Ficoll induced the B cell differentiation from mesenteric lymph node (MLN) cells but not from the PLN cells. This activation of MLN B cells with TNP-Ficoll was limited to normal DBA/2J mice and was absent in the MLN cells of X-linked immune defective CBA/N mice. Finally, there was good antibody response from the inguinal and lumbar lymph node cells after an intraperitoneal immunization with TNP-BA but not with TNP-Ficoll.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗