title: Influence of the polyclonal activation induced by Plasmodium chabaudi on ongoing OVA-specific B- and T-cell responses.
abstract: Infection by Plasmodium chabaudi results in polyclonal activation, massive proliferation and differentiation of lymphocytes with parasite-unrelated specificities. To verify if polyclonal activation includes experienced B and T lymphocytes and if it modifies pre-established cytokine and Ig-isotype patterns, mice were immunized with ovalbumin (OVA) in alum, a condition that favours T helper 2/immunoglobulin G1 (Th2/IgG1) responses, and infected with P. chabaudi 7 or 80 days later. Polyclonal activation markedly increased the number of anti-OVA Ig-secreting cells in the spleen, an effect more patent in mice infected 7 days after OVA immunization, but also evident in mice infected after 80 days. The Ig-isotype profile predefined by immunization was not qualitatively modified by polyclonal activation. Thus, although P. chabaudi infection preferentially induces IgG2a, the expanded anti-OVA response is dominated by IgG1. Polyclonal expansion of the anti-OVA response did not yield an enlarged memory B-cell pool that could be recalled months later by OVA boosting. Moreover, polyclonal activation of anti-OVA IgG1-secreting cells did not increase this antibody in serum, a probable consequence of the high Ig turnover observed during infection. When OVA-specific T-cell cytokines were evaluated, we observed an increase of both interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) in mice infected 7 days after immunization, whereas in those infected after 80 days, only IL-4 was augmented. These results suggest that polyclonal activation expands experienced B- and T-cell compartments, preserving their antibody and cytokine patterns.
authors.affiliation: Department of Immunology, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brazil.
authors.forename: L R
authors.initials: LR
authors.lastname: Sardinha
authors.forename: M R
authors.initials: MR
authors.lastname: D'Império Lima
authors.forename: J M
authors.initials: JM
authors.lastname: Alvarez
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis / Q000097:blood / Q000276:immunology; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D002999:Clone Cells / Q000276:immunology; D005260:Female; D007114:Immunization; D007117:Immunization, Secondary; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000097:blood / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis / Q000097:blood / Q000276:immunology; D007156:Immunologic Memory; D007371:Interferon-gamma / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin / Q000276:immunology*; D016788:Plasmodium chabaudi / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D013997:Time Factors
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D015847:Interleukin-4; D007371:Interferon-gamma; D010047:Ovalbumin