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1.
Medicina (B.Aires) ; 65(2): 103-107, 2005. tab, graf
Article in Spanish | LILACS | ID: lil-426089

ABSTRACT

Un paradigma clásico de la inmulogía plantea que para que ocurra cambio de isotipo en los anticuerpos es condición sine qua non la presentación del antígeno a un linfócito T colaborador por parte de una célula presentadora de antígenos. En el presente trabajo se diseñó un modelo animal, ratones BALB/c, de respuesta inmune frente a dos antígenos típicos. Se utilizo dextrán como antígeno T independiente (AgTI) y seroalbúmina bovina (SAB) como antígeno T dependiente (AgTD), y se estúdio la respuesta, analizando los isotipos de los anticuerpos específicos producidos. Los resultados obtenidos muestran que la respuesta a dextrán en presencia de SAB ocurre con cambio de isotipo (swith), essencialmente de IgM a IgG. Estos experimentos sugieren que la SAB genera un entorno bioquímico inductor de cambio de isotipo tanto en supropia via de procesamiento como en del dextrán. Los resultados señalan que la asociación exclusiva de los AgTDs con las respuestas em las que ocurre cambio de isotipo es incorrecta. Considerando el modelo propuesto resulta poco probable encontrar in vivo y en forma espontânea casos en los que los AgTIs ingreses al organismo aislados; en cambio, es mucho más probable que el ingreso ocurra conjuntamente con AgTDs, y en consecuencia ocurra cambio de isotipo.


Subject(s)
Cattle , Mice , Animals , Male , Female , Antigens, T-Independent/immunology , Dextrans/immunology , Immunoglobulin Class Switching/immunology , Serum Albumin, Bovine/immunology , Dextrans/pharmacology , Immunoglobulin Class Switching/drug effects , Immunoglobulin G/drug effects , Immunoglobulin G/immunology , Immunoglobulin M/drug effects , Immunoglobulin M/immunology , Mice, Inbred BALB C , Models, Animal , Serum Albumin, Bovine/pharmacology
2.
Ciênc. cult. (Säo Paulo) ; 46(5/6): 358-62, Sept.-Dec. 1994. ilus, graf
Article in English | LILACS | ID: lil-199863

ABSTRACT

T lymphocyte responses in vitro are not all-or-none choices to environmental stimulation, but follow at least three distinct patterns: full activation and expansion, anergy induction, and receptor-mediated suicide by apoptosis. In vitro model systems were devised to investigate the differential control of T cell responses by surface CD activation molecules, CD4+ T cells from T. cruzi-infected mice are severely impaired in their proliferative response to TCR stimulation. TCR stimulation leads to CD4+ T cell suicide by apoptosis, but CD3 stimulation is less efficient in this effect. Triggering of normal CD4 T cells through CD4 coincident with TCR activation, does not affect proliferative responses, but induces marked morphological changes in the T cells, which become adherent, form extended cytoplasmic projections, and acquire motile behavior. This response requires IL4 production, and can be markedly upregulated by exogenous IL4. Autoreactive CD4 T cell functioning can help syngeneic B cells to produce a TH2 pattern of immunoglobulin isotypes following stimulation by a thymus independent antigen. These results indicate that distinct patterns of functional behavior in vitro can be induced, depending both on the past experience of the T cell and on the exact array of stimulatory CD antigens engaged in the process of activation. The relevance of these constraints in generating variable behavior for immunoregulation is discussed.


Subject(s)
Humans , CD4-Positive T-Lymphocytes/immunology , Antigens, T-Independent/immunology , Cell Movement/immunology , Antibody Formation/immunology , Cell Adhesion Molecules/immunology , T-Lymphocytes
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