title: A Trypanosoma cruzi membrane protein shares an epitope with a lymphocyte activation antigen and induces crossreactive antibodies.
abstract: Chagas' disease results from the infection of the protozoan parasite Trypanosoma cruzi and affects several million people in South America. Several alterations of the immune response have been described in this disease, such as severe immunosuppression of both cellular and humoral responses and massive polyclonal stimulation with the generation of autoantibodies crossreacting with host cells and tissues. We have obtained monoclonal antibodies (mAbs) from T. cruzi-infected mice that recognized a 50/55-kD antigen (GP50/55) on the T. cruzi membrane, but not in other parasites of the family Trypanosomatidae. One of these GP50/55-specific mAbs (C10) crossreacts with a 28-kD antigen (p28) expressed on the membrane of greater than 85% of activated mouse T and B lymphocytes, after in vitro activation with concanavalin A, Salmonella typhosa lipopolysaccharide, phorbol dibutyrate ester, or antigen, and on several murine T and B lymphocyte cell lines. Human T and B lymphocytes also express upon activation with phytohemagglutinin or Staphylococcus aureus Cowan I (SAC) a similar antigen recognized by mAb C10, although in a lower proportion of cells (30-40%). Furthermore, this mAb was able to suppress mouse and human T and B cell proliferation to any of those stimuli. In addition, sera from chagasic patients and T. cruzi-infected mice, but not from control patients or littermates, contain antibodies that recognize a similar p28 antigen on B lymphocytes. Furthermore, the immunoglobulin fractions of some chagasic sera also suppress the proliferation of human T lymphocytes. These results suggest a possible pathological role of autoantibodies as an alternative mechanism for T. cruzi-associated immunosuppression.
authors.affiliation: Centro de Biología Molecular, Universidad Autónoma de Madrid, Cantoblanco, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Hernández-Munaín
authors.forename: J L
authors.initials: JL
authors.lastname: De Diego
authors.forename: A
authors.initials: A
authors.lastname: Alcina
authors.forename: M
authors.initials: M
authors.lastname: Fresno
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000917:Antibody Formation; D000953:Antigens, Protozoan / Q000032:analysis / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D014355:Chagas Disease / Q000276:immunology*; D003429:Cross Reactions; D000939:Epitopes / Q000032:analysis; D006801:Humans; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D013601:T-Lymphocytes / Q000276:immunology*; D014349:Trypanosoma cruzi / Q000276:immunology* / Q000302:isolation & purification
chemical_list: D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D000939:Epitopes; D008565:Membrane Proteins