CD4(+) T cell response to Leishmania spp. in non-infected individuals

T cell mediated immunity is known to play a central role ill the host respo nse to control intracellular pathogens. This work demonstrates the presence of specific CD4(+) T cells to Leishmania spp, antigens in peripheral monon uclear cells of naive individuals (normal volunteers from non-endemic regio ns). The responder population was expanded by generation of antigen-specifi c T cell lines, which were produced by repeated stimulation with fixed prom astigotes and autologous irradiated PBMC as antigen presenting cells. The l eishmania-T cell lines were shown to proliferate in response to different s pecies of the parasite (L. amazonensis, L, braziliensis, and L, donovani), but nut to other recall antigens such as Candida albicans or tetanus toxoid . A preferential expansion of IFN gamma 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 with in 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 bi the parasite and how infec tion impacts the naive T cell repertoire. (C) American Society for Histocom patibility and Immunogenetics, 2000. Published by Elsevier Science Inc.