Cd4+ T cell response to leishmania spp. in non-infected individuals

Abstract T cell mediated immunity is known to play a central role in the host response to control intra-cellular pathogens. This work demonstrates the presence of specific CD4 + T cells to Leishmania spp. antigens in peripheral mononuclear cells of naive individuals (normal volunteers from non-endemic regions). The responder population was expanded by generation of antigen-specific T cell lines, which were produced by repeated stimulation with fixed promastigotes and autologous irradiated PBMC as antigen presenting cells. The leishmania-T cell lines were shown to proliferate in response to different species of the parasite ( L. amazonensis , L. braziliensis , and L. donovani ), but not to other recall antigens such as Candida albicans or tetanus toxoid. A preferential expansion of IFNγ and IL-2 producing Th1-like T cells was observed. The leishmania-reactive cells were distributed between CD4 + CD45RA + (“naive”) and CD4 + CD45R0 + (“memory”) populations. Although limiting dilution analysis showed a precursor frequency 3 times lower within the naive compartment, similar numbers of T cell lines were derived from both purified subpopulations. This study using leishmania-specific CD4 + T cell lines produced from normal individuals should provide information on cellular immune responses that are triggered by the parasite and how infection impacts the naive T cell repertoire.