Biomedical subjects

A Coutinho

Publications and source records attributed to A Coutinho.

At least 199 records · Page 11Linked to original sources

PubMed1987

A functional idiotypic network of T helper cells and antibodies, limited to the compartment of "naturally" activated lymphocytes in normal mice.

As shown previously, idiotype (Id) sharing between anti-2,4,6-trinitrophenyl T helper (Th) cells and antibodies in BALB/c mice results from immunoglobulin (Ig)-dependent selection of the T cell repertoire. In contrast, a clonotype defined by the same F6(51) anti-Id antibody is expressed by C57BL/6 anti-(4-hydroxy-3-nitrophenyl)acetyl Th cells independently of Ig influences. We have now used these systems to test the hypothesis that Ig-dependent Th cell repertoire selection occurs in the compartment of "naturally" activated lymphocytes. "Naturally" activated or resting splenic L3T4+ cells were separated from normal BALB/c and C57BL/6 mice and tested, either directly or after in vitro priming, in hapten-specific helper assays for expression of the clonotope defined by the F6(51) anti-Id antibody. The results show the selective expression of the antibody-dependent T cell Id in the "naturally" activated helper cell compartment. In contrast, when the T cell Id is expressed in the absence of Ig-dependent selection, it is only detected in the resting helper cell repertoire. Furthermore, BALB/c "natural" IgM antibodies with anti-Id specificities similar to F6(51) show functionally relevant interactions with syngeneic "naturally" activated Th cells. These are also characterized by high paratopic/Id degeneracy, as compared to helper cells obtained by conventional immunization. These results demonstrate repertoire differences between the set of (resting) lymphocytes participating in immune responses, vs. those "internally" activated in normal individuals. They also suggest the importance of Id network interactions in the compartment of "naturally" activated T and B cells.

Animals↗

PubMed1987

The majority of "natural" immunoglobulin-secreting cells are short-lived and the progeny of cycling lymphocytes.

Treatment of mice with hydroxyurea to selectively kill all cycling cells has been used to study population dynamics and life expectancy of "natural" immunoglobulin-secreting cells in the bone marrow and spleen of nonimmunized animals. The results show that 50 to 90% of those cells are eliminated 2 to 3 days after one cycle of hydroxyurea administration, demonstrating their recent origin from cycling precursors. Using a protocol of long-term hydroxyurea treatment which abrogates cell production from the cycling precursors compartments, it was shown that "natural" immunoglobulin-secreting cells have a very short half renewal time, in the range of 15-60 h.

Aging↗

PubMed1987

"In vivo" activated splenic T cells are refractory to interleukin 2 growth "in vitro".

Naturally activated T lymphocytes present in normal mouse spleen were studied for direct reactivity to interleukin 2 (IL 2) and for binding of anti-IL 2 receptor (IL 2R) antibodies or radiolabeled IL 2. The majority of large-sized splenic T lymphocytes are IL 2R-; thus, at the most one third of large L3T4+ T cells and of large Lyt-2+ T lymphocytes bind (weakly) anti-IL 2R antibodies; furthermore, most IL 2R+ cells in the normal spleen are actually Lyt2-, L3T4-. Total large splenic lymphocytes do not express more than an average of 150 high-affinity IL 2R/cell. Such cell populations, as well as large T cells enriched from them, failed to proliferate exponentially in the presence of recombinant IL 2, but did not suppress the IL 2-dependent proliferative responses of small T cells activated in the same cultures. In vivo activation of small T cells, in concanavalin A-treated irradiated syngeneic hosts, also results in refractoriness to growth in recombinant IL 2. In addition, these cells remain insensitive to ligands such as concanavalin A, phorbol myristate acetate and ionomycin, in the presence or absence of IL 2. These results question the role of IL 2 as a growth factor of in vivo activated splenic T lymphocytes, or else indicate that most of these are terminally differentiated cells.

Animals↗

PubMed1987

A common idiotope on T cell receptors and antibodies expressed in the absence of network selection.

The monoclonal antibody F6(51), directed to an idiotope of MOPC 460-like anti-1,4,6-trinitrophenl (TNP) antibodies produced in IgHa mouse strains, identifies in helper T cells from C57BL/6 (IgHb) mice with (4-hydroxy-3-nitrophenyl)acetyl (NP)-self specificity, a clonotypic determinant functionally and biochemically associated with the specific T cell receptor. The expression of this antibody-related T cell clonotype in C57BL/6 mice, although "recurrent", is independent of network selection, as shown by its presence in B mice suppressed from birth with anti-mu antibodies, and in IgH-congenic mouse strains. These results indicate aleatory cross-reactivity between T cell receptors and antibodies and command caution in network interpretations for "idiotype sharing".

Animals↗

PubMed1987

Turning (Ir gene) low responders into high responders by antibody manipulation of the developing immune system.

The ability of helper T cells directed against trinitrophenyl-modified syngeneic spleen cells to recognize low-hapten densities on target cells is under major histocompatibility complex-linked Ir gene control. Thus, BALB/c (H-2d) mice are low responders while H-2 congenic BALB.C3H (H-2k) mice are high responders. Immunization of adult BALB/c mice with the monoclonal antibody F6(51), directed to shared idiotopes by anti-trinitrophenyl antibodies and clonal receptors on anti-trinitrophenyl-self helper T cells, leads to the production of high titers of circulating idiotype, has no influence on helper T cell idiotypic profiles, but shifts to a high-responder phenotype the ability of helper T cells to recognize low-hapten densities. These effects on Ir gene phenotype are even more striking in untreated progenies from F6(51)-immunized BALB/c females, which are better responders than genetically high-responder BALB.C3H mice, although completely different in the expression of the F6(51)-defined clonotype. The general significance of these findings on Ir gene-directed T-cell repertoire selection is discussed, for they constitute formal evidence against antigen-presentation as a mechanism of Ir gene effects and strong support for the importance of maternal influences on the development of T-cell repertoires.

Animals↗

PubMed1987

The role of I-A/E molecules in B-lymphocyte activation. II. Mechanism of inhibition of the responses to lipopolysaccharide by anti-I-A/E antibodies.

We have previously demonstrated that monoclonal anti-I-A/E antibodies inhibit B-cell responses to lipopolysaccharide (LPS). In the present report, the inhibitory effects were shown to be carried out directly on B cells, and to be totally independent of the LPS concentration used, thereby showing that antibodies do not mediate their effect through blocking of accessory cells or steric hindrance of LPS-receptors. Of the three different phases in B-cell activation/induction, proliferation, and maturation, induction was shown to be the most sensitive to inhibition by anti-I-A/E antibodies. Thus, kinetic studies showed that anti-I-A/E antibodies are only inhibitory for the first 16 h of LPS activation, after which B cells can no longer be inhibited by these antibodies. Class II MHC molecules appear, therefore, to be part of a membrane molecular complex which regulates delivery of activation signals to resting B cells. Since it was also shown that this time period corresponds approximately to the time required for B cells to express functional reactivity to growth factors, we suggest that anti-I-A/E antibodies act on resting B lymphocytes to inhibit mitogen-dependent induction of growth receptor expression.

Animals↗

PubMed1987

Idiotypic multireactivity of 'natural' antibodies. 'Natural' anti-idiotypes also inhibit helper cells with cross-reactive clonotypes.

One hundred and twenty IgM-secreting hybridomas derived from unmanipulated 6-day-old BALB/c mice were screened for reactivity with the prototype idiotypic and anti-idiotypic monoclonal antibodies, defining three well established systems, namely TEPC 15:10/13-15, J558:CD3.2, and MOPC 460:F 6(51). Up to 25% of all IgM antibodies reacted with at least one of the six specific ligands, half of the latter being 'monospecific', the others reacting with two or more antibodies. A detailed analysis of the four most multi-reactive clones showed individually specific patterns of reactivity and revealed reactions of the same IgM molecule in idiotypic systems previously studied independently. Furthermore, when tested for functional interactions with syngeneic helper T cells expressing MOPC 460-like clonotypes, one of these antibodies was found to inhibit effector helper activity. The results show the existence of 'natural antibodies' with idiotypic reactivities related to recurrent clonotypes in the strain. They may be either 'specific' or 'multireactive', and might connect idiotypes on T and B cells and on antigenic systems so far studied independently.

Animals↗

PubMed1987

Specific treatment of advanced schistosomiasis liver disease in man: favourable results.

One hundred eighty-four patients with hepatosplenic schistosomiasis mansoni from the northeast of Brazil were studied. All were treated with a single dose of Oxamniquine or Praziquantel, and were observed over 6 to 12 months. Special attention was given to the evolution of severe hepatopathy. Favourable results were obtained, particularly with the compensated hepatosplenic form. Hepatic function showed great improvement. Hepatomegaly and splenomegaly were significantly reduced in size, to a greater or lesser extent, in the great majority of patients. The implications of the results obtained are considered below.

Adolescent↗

PubMed1987

Sporadic idiotypic cross-reactivities between antibodies and T helper cells: one example of aleatory expression of T cell idiotypes.

Idiotypic cross-reactivities between T and B cell receptors have been taken in the past to suggest VH-gene expression by both types of lymphocytes. More recently, after the molecular characterization of TcR, those observations were reinterpreted to indicate idiotypic network regulation, operating to select cross-reactive idiotypes in both B and T cell compartments. In support of these views, it has been shown that T cell expression of idiotypes is controlled by IgH-linked genes and markedly altered in B cell-deprived mice, and that T cells "learn" idiotype expression from the B cell compartment in the first few weeks of life. In most of these studies, aleatory idiotype cross-reactivities have not been sufficiently considered. Given the large diversity of antibodies and TcR, and the degeneracy of antibody-ligand interactions, it could be expected that a (monoclonal) anti-idiotypic reagent prepared against an antibody idiotope will always "cross-react" with some TcR variable regions. If these will be "major" T cell clonotypes, situations of idiotype sharing by B and T cells can be found which indicate neither VH-gene expression by T cells nor idiotypic network regulation. We report here one example of such aleatory expression of antibody idiotypes by T lymphocytes. A monoclonal anti-idiotypic antibody directed to anti-TNP antibodies of BALB/c mice specifically inhibits the growth and effector activity of C57BL/6 anti-NP-self helper T cells, while failing to interact with either BALB/c anti-NP-self or C57BL/6 anti-TNP-self helper cells. The clonotypic nature of these interactions could also be demonstrated by the specific induction of IL-2 production in the appropriate helper T cells by the anti-idiotypic antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Immunocompetent autoreactive B lymphocytes are activated cycling cells in normal mice.

Frequencies of B cell clonal precursors producing antibodies that react with mouse thyroglobulin, mouse erythrocytes, beef hemoglobin, KLH, and sheep erythrocytes were determined by limiting dilution analyses among small, resting lymphocytes, and among large activated cells from normal adult mice. While frequencies of clones reacting with external antigens were equally distributed in large and small B cells, most, if not all, autoreactive B lymphocytes were found in the large cell fraction. Analysis of antithyroglobulin hybridomas isolated from normal mice revealed dissociation constants ranging from 10(-6) to 5-6 X 10(-7). Treatment of normal donors with antimitotic drugs dramatically decreases the frequencies of autoreactive B cells, but not those of B lymphocytes reacting with external antigenic molecules. Taken together, these experiments show that immunocompetent, autoreactive B lymphocytes are activated and cycling cells in the peripheral lymphoid tissues of normal individuals.

Animals↗

PubMed1986

Persistence of polyclonal B cell activation with undetectable parasitemia in late stages of experimental Chagas' disease.

The polyclonal B cell responses induced by Trypanosoma cruzi infection last for at least 6 mo after the inoculation of the parasites. In the acute phase of the disease, B cells from spleen and lymph nodes are largely stimulated, whereas a decrease in bone marrow PFC is observed. As the disease progresses, the numbers of Ig-secreting cells in the spleen, lymph nodes, and bone marrow are all enhanced. The isotype distribution of PFC, however, remains unvariable along the course of the infection, and it is characterized by the predominance of IgG2a- and IgG2b-secreting cells. No striking difference in the isotype pattern of resistant and susceptible strains of mice was observed. The continuous and long-lasting B cell stimulation generated during the infection may have important consequences in the pathology of Chagas' disease.

Acute Disease↗

PubMed1986

The high idiotypic connectivity of "natural" newborn antibodies is not found in adult mitogen-reactive B cell repertoires.

Unselected IgM-secreting hybridoma collections were established either from unprimed naturally activated newborn spleen cells or from mitogen-stimulated adult B cells. These were then screened for reactivity with a panel of monoclonal anti-idiotypic antibodies and haptens. While the finding of hapten-specific antibodies was equally frequent in either collection, newborn antibodies reacted at least 10 times more frequently with the anti-idiotypic reagents. The reactivity patterns of individual antibodies readily demonstrated the overall specificity of these V-region interactions. Since some of the idiotopes screened are characteristically not expressed in immune responses by the strains analyzed, and are in fact not expressed in the adult induced hybridoma collection, we explain these findings by a unique property of the set of natural (newborn) antibodies i.e. the high levels of idiotypic connectivity previously described within this repertoire.

Age Factors↗

PubMed1986

The role of immunoglobulin receptors in "cognate" T-B cell collaboration.

The functional effects of anti-Ig antibodies have been investigated, using an experimental system where B cell activation is brought about by direct and specific interactions with T helper (Th) cells without participation of surface Ig receptors on the responding B cell. We have used Th cell lines and clones directed to class II major histocompatibility complex antigens of the responding B cells, and titrated into cooperative cultures either purified rabbit anti-mouse mu, or monoclonal mouse anti-delta antibodies. Both types of antibodies greatly enhanced B lymphocyte responses to suboptimal concentrations of functionally efficient Th cells, while they had no effect in cultures containing optimal Th:B cell ratios. In contrast, helper activity by low efficiency Th was, at all Th:B cell ratios, enhanced by appropriate concentrations of anti-Ig antibodies. Anti-Ig effects were exclusively observed when B cells were the targets for "cognate" recognition by Th cells. We conclude that ligand binding to surface Ig receptors on resting B cells fails, in our experimental conditions, to overcome "linked" collaboration, but it greatly facilitates productive Th-B cell interactions. Whatever the mechanisms underlying this facilitation, the observations imply roles of surface Ig in Th-dependent B lymphocyte activation other than either passive "focusing" of antigen or activation into reactivity to soluble, unspecific factors.

Animals↗

PubMed1986

The basis for major histocompatibility complex (MHC) and immunoglobulin gene control of helper T cell idiotopes.

BALB/c helper T cells, prepared against 2,4,6-trinitrophenyl (TNP)-derivatized syngeneic spleen cells, fail to recognize other hapten modifications [(4-hydroxy-3-nitrophenyl)acetyl, fluorescein isothiocyanate] of syngeneic cells, as well as TNP-derivatized cells from major histocompatibility complex-congenic donors. T helper cell interactions with "presenting" cells and "target" B lymphocytes are inhibited by monoclonal antibodies directed either to the hapten or to I-A molecules on target cells. Helper activity is also inhibited by monoclonal anti-idiotypic antibodies directed to an idiotope expressed by the TNP-binding myeloma protein MOPC460, but not by soluble TNP-protein conjugates. The study of congenic mouse strains revealed that while the fine specificity of TNP recognition and the quantitative levels of M 460 idiotope expression are I-A linked, the expression of the M 460 idiotope by helper cells is controlled by IgCh-linked genes. Absence of anti-idiotope inhibition of helper cells prepared in anti-mu-suppressed mice suggests, however, that immunoglobulin idiotype expression by T cells results from network interactions selecting available lymphocyte repertoires which operate before antigenic stimulation.

Animals↗

PubMed1986

Effector functions and specificities of normal murine T cells stimulated by syngeneic blasts.

Large numbers of syngeneically stimulated T cells are easily obtained by stimulation of splenic T cell populations with irradiated lipopolysaccharide (LPS) blasts. Thus, proliferative T cell responses were obtained after stimulation with allogeneic LPS blasts, concanavalin A (Con A) blasts, normal spleen cells or peritoneal macrophages while only LPS and Con A blasts were competent syngeneic stimulators. The cytolytic activity of T cells stimulated with allogeneic LPS blasts was H-2 specific, while that of T cells stimulated with syngeneic LPS blasts was often completely nonspecific, and higher for LPS than for Con A blast target cells. In other experiments, "self" H-2K- and I-A-specific cytotoxic T cells were obtained, without apparent reasons for the development of either type of cytolytic cells. Stimulation of Lyt-2- T cells with syngeneic LPS blasts led to the generation of T helper effector cells which induced normal B cell proliferation in an H-2 restricted manner. This restriction was over-come, the proliferative responses were augmented and plaque-forming cell responses generated, through addition of Con A to the cultures. The results imply the ability of B blasts to induce stimulation of syngeneic T cells, and generation of effector cells displaying cytolytic and helper activity. This phenomenon might play a role in the regulation of the immune system.

Animals↗

PubMed1986

Autonomous activation of B and T cells in antigen-free mice.

The spleen of adult antigen-free mice contains a sizable proportion (5-15%) of activated cells in all lymphocyte sets, as marked by the membrane expression of immunoglobulins, L3T4 and Lyt-2 antigens. The frequency of activated cells is very high in early post-natal life, and reaches adult levels by 6 weeks of age when it is comparable to that observed in healthy unmanipulated mice raised in conventional conditions. The effector B cell compartment is quantitatively similar in antigen-free mice and specific pathogen-free mice, but the former is deficient in isotype diversification, since IgG- and IgA-secreting cells are drastically reduced. The effector T cell compartment is slightly reduced in number, but is equally competent in providing help or suppression of syngeneic B cells. The results indicate the existence of a compartment of the immune system displaying autonomous self-determined activity which is predominant early in life. This compartment, physically localized to the spleen, appears to be distinct from an antigen-dependent compartment which is essential for the development of peripheral lymphoid organs draining sites of "natural" environmental immunization.

Animals↗

PubMed1986

The immune response to bacterial dextrans. III. Ontogenic development and strain distribution of specific clonal precursors.

The frequencies of B512 dextran (Dex)-specific B cell precursors were determined by limiting dilution analysis in a number of mouse strains originally described as "high responder", "low responder" and "nonresponder" to this antigen. No significant difference in the frequencies of Dex-specific precursors was found in C57BL/6, B10.BR, C3H/Tif, BALB/c and A/Sn adult mice. Together with the large intra-strain variability in the magnitude of anti-Dex PFC responses in vivo, these results established that differential reactivity in vivo cannot be ascribed to genetically controlled absence or wide variation in the frequency of Dex-specific immunocompetent precursors. A similar analysis of the Dex-specific precursor frequency was carried out in C57BL/6 mice between 1 week and 3 months of age. While no Dex-specific antibody response was detected in vivo before the age of 3 weeks, clonal precursor analysis revealed that the appearance of these specificities parallels the development of competent (IgM-producing) B lymphocyte clonal precursors, such that no significant difference in absolute frequencies of Dex-specific precursors could be observed among these age groups. This is interpreted to suggest that the late development of the Dex-specific antibody responses is regulatory rather than due to late rearrangement and activation of the appropriate V genes and a sequential expression of antibody specificities in ontogenic development.

Age Factors↗

PubMed1986

Maternal transmission of idiotypic network interactions selecting available T cell repertoires.

Up to 75% of 2,4,6-Trinitrophenyl (TNP)-self-specific helper T cells from normal BALB/c mice share a clonotypic determinant with the anti-TNP myeloma protein MOPC 460, recognized by the monoclonal antibody F6(51). Immunization of adult BALB/c mice with the MOPC 460 idiotype (Ab2 mice) leads to high titers of circulating anti-idiotypic antibodies but has no influence on the expression of the T cell clonotype. In contrast, TNP-self-specific helper cells prepared in progenies from Ab2 females, or in BALB/c mice treated as neonatals with anti-idiotypic antibodies, fail to express the corresponding T cell clonotype when immunized as adults. These results demonstrate the idiotype-dependent selection of T cell repertoires early in life and their stability in adults.

Animals↗