title: CD4 T cell activation by B cells in human Leishmania (Viannia) infection.
abstract: BACKGROUND
  An effective adaptive immune response requires activation of specific CD4 T cells. The capacity of B cells to activate CD4 T cells in human cutaneous leishmaniasis caused by Leishmania (Viannia) has not been evaluated.
  
  
  METHODS
  CD4 T cell activation by B cells of cutaneous leishmaniasis patients was evaluated by culture of PBMCs or purified B cells and CD4 T cells with Leishmania panamensis antigens. CD4 T cell and B cell activation markers were evaluated by flow cytometry and 13 cytokines were measured in supernatants with a bead-based capture assay. The effect of Leishmania antigens on BCR-mediated endocytosis of ovalbumin was evaluated in the Ramos human B cell line by targeting the antigen with anti-IgM-biotin and anti-biotin-ovalbumin-FITC.
  
  
  RESULTS
  Culture of PBMCs from cutaneous leishmaniasis patients with Leishmania antigens resulted in upregulation of the activation markers CD25 and CD69 as well as increased frequency of CD25hiCD127- cells among CD4 T cells. Concomitantly, B cells upregulated the costimulatory molecule CD86. These changes were not observed in PBMCs from healthy subjects, indicating participation of Leishmania-specific lymphocytes expanded in vivo. Purified B cells from these patients, when interacting with purified CD4 T cells and Leishmania antigens, were capable of inducing significant increases in CD25 and CD69 expression and CD25hiCD127- frequency in CD4 T cells. These changes were associated with upregulation of CD86 in B cells. Comparison of changes in CD4 T cell activation parameters between PBMC and B cell/CD4 T cell cultures showed no statistically significant differences; further, significant secretion of IFN-γ, TNF-α, IL-6 and IL-13 was induced in both types of cultures. Additionally, culture with Leishmania antigens enhanced BCR-mediated endocytosis of ovalbumin in Ramos human B cells.
  
  
  CONCLUSIONS
  The capacity of B cells specific for Leishmania antigens in peripheral blood of cutaneous leishmaniasis patients to activate CD4 T cells and induce cytokine secretion is similar to that of all cell populations present in PBMCs. This capacity implicates B cells as a plausible target for modulation of the immune response to Leishmania infection as a therapeutic strategy.
authors.affiliation: Centro Internacional de Entrenamiento e Investigaciones Médicas (CIDEIM), Cali, Colombia. derodriguez@udla.edu.ec.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rodriguez-Pinto
authors.forename: Nancy Gore
authors.initials: NG
authors.lastname: Saravia
authors.forename: Diane
authors.initials: D
authors.lastname: McMahon-Pratt
mesh_terms: D000328:Adult; D000368:Aged; D001402:B-Lymphocytes / Q000276:immunology*; D001710:Biotin / Q000737:chemistry; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003105:Colombia / Q000453:epidemiology; D005260:Female; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D005786:Gene Expression Regulation; D006801:Humans; D007075:Immunoglobulin M / Q000737:chemistry; D007371:Interferon-gamma / Q000276:immunology; D015850:Interleukin-6 / Q000276:immunology; D007892:Leishmania braziliensis / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000097:blood* / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010047:Ovalbumin / Q000737:chemistry; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D055815:Young Adult
chemical_list: D007075:Immunoglobulin M; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D001710:Biotin; D007371:Interferon-gamma; D010047:Ovalbumin; D016650:Fluorescein-5-isothiocyanate