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Biomedical subjects

A Coutinho

Publications and source records attributed to A Coutinho.

At least 163 records · Page 9Linked to original sources
PubMed1989

Evidence for a functional idiotypic network among natural antibodies in normal mice.

We monitored in normal adult BALB/c mice the serum concentrations of four natural IgM antibodies, two of which show idiotypic complementarity in in vitro assays. In each individual, serum concentration of all four idiotypes were found to fluctuate in complex dynamical patterns with low correlation. The spectral power of some such patterns was found to be compatible with the existence of a chaotic regime. Groups of normal adult mice were injected intravenously with low (10 ng) or moderate (10 micrograms) doses of either of the two complementary idiotypes in saline. This treatment resulted in a pronounced inhibition of the fluctuation in the serum concentration of both complementary idiotypes for periods up to 3 months. Such compensations were not detected for the two unrelated natural idiotypes and were specifically induced, for they did not occur following the injection of unrelated antibodies. These results indicate the functional operation of an idiotypic network among natural antibodies.

Animals↗
PubMed1989

Preferential expansion of Ly-1 B and CD4- CD8- T cells in the polyclonal lymphocyte responses to murine T. cruzi infection.

Acute murine infection with T. cruzi results in polyclonal lymphocyte responses manifested by blast transformation of a large fraction of B, CD4+, and CD8+ cells. We describe here the finding of significant increases in the splenic representation of minor populations, Ly-1 + B cells and CD4-CD8- T cells. These lymphocyte populations might play an important role in the host response, as shown by T. cruzi infection of hosts that had been lethally irradiated and reconstituted with autologous bone marrow. Under these conditions, the splenic polyclonal PFC responses are nearly abrogated, and not restored by the transfer of syngeneic peritoneal cells which, however, reconstitute T15 idiotype production in the same hosts. Control levels of PFC responses, however, are reconstituted by transfer of syngeneic splenic T cells. Since bone marrow-reconstituted animals contain normal numbers of CD4+ and CD8+ T cells which are actually activated by infection, these results suggest the participation of other T cell populations in the host response to infection, as also suggested by the marked increases in T cell receptor gamma and delta messages detected in the spleen of infected animals. The implications of these findings in immunopathology of Chagas' disease are discussed.

Animals↗
PubMed1989

Expression of antibody V-regions is genetically and developmentally controlled and modulated by the B lymphocyte environment.

In this study we performed a comprehensive analysis of VH family usage in the emergent, available and actual repertoires of neonatal and adult BALB/c and C57BL/6 (B6) mouse strains. For this purpose we used an in situ hybridization technique that allows the detection of VH-gene expression at a single cell level. We have found that VH gene expression in neonatal mice is determined by a non-random position-dependent process which favours the utilization of the most D-proximal VH 7183 family. The preferential usage of the 7183 family is also characteristic of early differentiating bone marrow B cells of adult BALB/c mice. At different stages of ontogeny and B cell development VH family repertoires evolve in a strain-specific manner, with significantly higher utilization of the VH J558 family in B6 mice. In the peripheral immunocompetent cell pool, local environmental factors can further modulate VH family expression and lead to increased representation of the VH J558 family in peripheral lymph nodes and of the VH X-24 family in intestinal Peyer's patches. In conclusion, our present results indicate that VH family usage is controlled by genetic, developmental and environmental factors and suggest that selection of antibody repertoires can occur at multiple stages in B cell development.

Animals↗
PubMed1989

A model system for the analysis of B-cell activation and effector T-cell functions. T cell-dependent B-cell responses facilitated by anti-I-A antibodies.

We have attempted to develop an in vitro system where polyclonal B lymphocyte responses could be induced in 'antigen-like' conditions, that is, where surface immunoglobulin-dependent binding mediates interaction with a mitogen. Monoclonal anti-mu and anti-delta antibodies were covalently bound to lipopolysaccharide (LPS) and these complexes were shown to display mitogenic activity. Polyclonal plaque-forming cell (PFC) responses, however, were diminished in cultures stimulated by anti-mu-LPS (but not by anti-delta-LPS) indicating that 'anti-mu inhibition' of terminal B-cell differentiation also applies to 'specific' antibody responses. Moreover, the analysis of the functional activity of monoclonal antibodies to major histocompatibility complex (MHC) class II molecules revealed a surprising synergy between low, non-stimulatory concentrations of anti-mu-LPS (but not anti-delta-LPS) with anti-I-A antibodies. These responses are T-cell dependent and synergy with anti-mu-LPS conjugates can also be obtained with 'naturally' activated CD4+ cells isolated from normal donors. A model of molecular and cellular interactions was derived, which accounts for the present findings and is applicable in antigen-dependent lymphocyte collaboration.

Adjuvants, Immunologic↗
PubMed1989

The immune response to bacterial dextrans. VI. No correlation between the frequency of cells expressing a major anti-dextran idiotype and the idiotype profiles of specific antibody responses.

C57BL/6 mice respond to Dextran B512 (Dex) with a predominant idiotype (Id) (17-9) while no such Id-positive antibodies are identified in the specific antibody response of BALB/c mice. We used limiting dilution systems to determine the absolute frequencies of clonal B-cell precursors producing the 17-9 Id in these two mouse strains and analysed the correlation between Id-expression and antibody activity at the clonal level. The results show very similar frequencies of anti-Dex and Id-positive B cells in both strains, but C57BL/6 mice contained fourfold higher frequencies of Dex-specific clonal precursors which are Id-positive. This kind of clone, although not used in the specific response of BALB/c mice, constitute roughly 20% of their anti-Dex repertoire and they are readily induced in this strain. Thus, immunization of both strains with anti-idiotypic antibodies results in the production of Id-positive anti-Dex antibodies with serum titres that directly correlate with precursor frequencies. The results show, therefore, that the section of clonal repertoires utilized in a primary immune response varies with the immunogen, even if thymus-independent. These observations are discussed in the context of the genetic controls of anti-Dex antibody responses and on the general question of the utilization of available antibody repertoires in immune responses.

Animals↗
PubMed1989

Differential binding of natural monoclonal antibodies to the surface of fixed or living cells.

A few hundred monoclonal antibodies derived from normal mice were tested for binding to cell surface antigens in one T-cell hybridoma and one I-Ek-transfected fibroblast cell line. The assay, which is suitable for large screenings, used glutaraldehyde-fixed cells followed by immunoenzymatic detection of immunoglobulin. Of the 331 antibodies tested, 75 showed significant binding, not only on these cells, but also on a macrophage, fibroblast, thymoma, and pre-B cell line, and on normal syngeneic and allogeneic thymocytes. If the assay was modified so as to use live cells in a simplified ELISA on living cells, only 10 of 253 antibodies were found to be positive with the T-cell hybridoma line and 7 with the transfected fibroblast cell line. In both sets of conditions, about 75% of the positive antibodies were found to be 'multireactive' after being tested on a panel of antigens. In contrast, conventional 'immune antibodies' to cell surface antigens could be tested by routine methods in either type of assay. We conclude that, while glutaraldehyde fixation does not affect the reactivity of conventional antibodies, this technique is inappropriate for testing the binding of natural antibodies to cell surface antigens.

Animals↗
PubMed1989

Elevation of laminin and beta-subunit of prolyl 4-hydroxylase in the sera of human subjects with Schistosomiasis mansoni.

Serum levels of several markers for liver fibrosis were measured utilizing three groups of human subjects related with schistosomiasis mansoni in northeast Brazil; (1) 20 Schistosoma mansoni egg-positives, who have never been administered with anti-schistosomal drugs, (2) 29 egg-negative inhabitants in the endemic area of schistosomiasis, and (3) 23 egg-negative Japanese immigrants in the non-endemic area. None of these sera were positive for antibody to the surface antigen of human hepatitis B (HBs) and circulating HBs antigen. There was no significant difference in the serum levels of N-terminal peptide of procollagen type-III between the egg-positive subjects and either of the egg-negative Brazilian or Japanese immigrants, whereas the mean value of serum laminin significantly increased in the egg-positive subjects. A significantly higher concentration of serum immunoreactive beta-subunit of prolyl 4-hydroxylase (IR beta PH) was also observed in the egg-positive subjects only in comparison with that of the egg-negative Brazilian. Serum laminin and IR beta PH concentrations of the egg-positive subjects did not correlate with the absorbance of enzyme-linked immunosorbent assay (ELISA) which utilized crude antigens isolated from schistosome adults or eggs. No significant difference in these two parameters was observed between two subgroups of the egg-negative Brazilian or Japanese immigrants divided according to the serological data by ELISA. These findings suggest that serum laminin and IR beta PH levels are worth further evaluation for their usefulness as the marker for liver fibrosis in schistosomiasis.

Adolescent↗
PubMed1988

Selection of antibody repertoires by anti-idiotypes can occur at multiple steps of B cell differentiation.

These experiments were designed to evaluate whether alterations in Id expression after anti-Id treatments result from direct modulation of Id-producing B cells, and whether idiotypic selection operates in bone marrow or spleen B cells. By using the NPb Id model, we have studied the functional behavior of isolated LPS-reactive B cells transferred from B6 mice into histocompatible LPS-NR B10.Cr hosts and primed with LPS conjugates of anti-Id antibodies. We have found that previous anti-idiotypic manipulation of host mice by neonatal administration of suppressive doses of Ac 38 antibodies, or adult injection of enhancing doses of Ac 146 antibodies, modulated the T cell-independent Id response of either immature bone marrow or mature splenic responding cells, transferred from normal, untreated donors. These results are interpreted to suggest that selection of antibody repertoires by anti-Id may occur at multiple steps of B cell differentiation.

Animals↗
PubMed1988

Immunological consequences of HIV infection: advantage of being low responder casts doubts on vaccine development.

Immunosuppression in AIDS might be due to the immune response rather than to the pathogenicity of the virus. The basis of the immunosuppression could be molecular mimicries involving viral gp-110, CD4 molecules, antibodies, and CD4-acceptor sites. Whether an individual develops auto-immunosuppressive responses or mounts a harmless defence against (or coexists with) the virus follows the general rules of lymphocyte repertoire selection. MHC and V region genes and other polymorphic loci, together with the previous state of the immune system, particularly at early developmental periods, are factors that influence the response. Vaccination against gp 110-HIV might thus protect against infection but at the same time cause auto-immunosuppression and disease.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Inverse correlation between the utilization of an idiotype in specific immune responses and its representation in pre-immune "natural" antibodies.

Previously we have characterized an idiotype (Id) that accounts for half of all specific anti-dextran B512 (Dex) antibodies in C57BL/6 mice. BALB/c mice produce the same Id in normal, pre-immune sera but fail to use it in antibody responses to Dex, although Id+ anti-Dex antibodies can be induced in this strain by anti-Id immunization. By limiting dilution analysis of B cell clonal precursors, we show here that the frequencies of Id+ B cells are comparable in both strains, but their state of activity is sharply distinct: while all Id+ B cells are small, resting lymphocytes in C57BL/6 mice, they are all large, naturally activated cells in BALB/c mice. The suggestion that naturally activated cells are poorly engaged in specific responses was supported by the delayed and lower Id+ responses obtained in BALB/c mice when they are immunized, in parallel with C57BL/6 animals, with a conjugate of anti-Id antibodies and lipopolysaccharide. Finally, C57BL/6 responder mice were found to closely reproduce the normal BALB/c situation, if analyzed 3 months after anti-Id priming: they produce low levels of serum Id and all Id+ B cells are in the large lymphocyte compartment. Upon immunization these animals develop serum Id+ responses that are undistinguishable from low-responder BALB/c mice. The relevance of these observations for the questions of physiologic self-reactivity is discussed.

Animals↗
PubMed1988

B cell participation in the recursive selection of T cell repertoires.

Normal BALB/c mice produce 2,4,6-trinitrophenyl (TNP)-I-Ad specific T helper (Th) cells expressing a receptor heterodimer which share with anti-TNP antibodies an idiotope defined by the F6(51) anti-idiotypic antibody. Expression of this Th idiotype is controlled by major histocompatibility complex and immunoglobulin heavy chain-linked genes and results from antibody-dependent selection of T cell repertoires (Martinez-A. et al., Eur. J. Immunol. 1986. 16: 417). We now present evidence for the recursive nature of T----B cell repertoire selection and suggest that perinatal B cells, present in adult peritoneal cavity, operate in the early phases of this process. Thus, the Th idiotype is absent in BALB/c mice which are either suppressed from birth with anti-mu antibodies, or reconstituted with autologous bone marrow after lethal irradiation as adults. Supplementation of bone marrow reconstitution with syngeneic Thy-1-, Ly-1+ peritoneal B cells, however, selects Th cell repertoires that are undistinguishable from normal mice as to expression of the F6(51) clonotype. This effect is lost after depletion of Ly-1+ cells in the reconstituting Thy-1- peritoneal cell population. Interestingly, large in vivo "naturally" activated Ly-1- splenic B cells can also reconstitute Th idiotype expression if they are isolated from normal, but not from athymic, nude donors. However, transfer of normal large splenic T cells to adult nude mice "educates" the splenic "large B cell" compartment in these animals such that they acquire the ability to recursively select, upon transfer to bone marrow reconstituted recipients, the Th clonotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗