title: Evidence for T Cell Help in the IgG Response against Tandemly Repetitive Trypanosoma cruzi B13 Protein in Chronic Chagas Disease Patients.
abstract: The tandemly repetitive Trypanosoma cruzi B13 protein is an immunodominant antigen among Chagas disease patients. Such repetitive domains may behave as T-independent antigens. However, T cells can recognize B13 epitopes in an HLA class II-restricted fashion and could potentially provide cognate T cell help and boost antibody titers. We assessed whether the presence of HLA class II molecules able to present B13 epitopes to T cells could affect anti-B13 IgG levels in a cognate fashion, in both major clinical forms of chronic Chagas disease. We found no difference between anti-B13 IgG antibody levels between patients carrying HLA class II molecules associated to T cell responses or other alleles. The predominant anti-B13 IgG subclass was IgG1, with negligible IgG2, suggesting a T-dependent, noncognate help for antibody production. In addition, the finding of increased anti-B13 IgG levels in sera from CCC patients indicates that clinical presentation is associated with increased anti-B13 antibody levels.
authors.affiliation: Laboratory of Immunology, Heart Institute (InCor), School of Medicine, University of São Paulo, 05403-900 São Paulo, SP, Brazil.
authors.forename: Marcia
authors.initials: M
authors.lastname: Duranti
authors.forename: Ludmila
authors.initials: L
authors.lastname: Camargo
authors.forename: Gabriel
authors.initials: G
authors.lastname: Victora
authors.forename: Barbara
authors.initials: B
authors.lastname: Ianni
authors.forename: Paula
authors.initials: P
authors.lastname: Buck
authors.forename: Charles
authors.initials: C
authors.lastname: Mady
authors.forename: Jorge
authors.initials: J
authors.lastname: Kalil
authors.forename: Bianca
authors.initials: B
authors.lastname: Zingales
authors.forename: Edecio
authors.initials: E
authors.lastname: Cunha-Neto