IFN-γ-producing CD45RA⁺ CD8⁺ and IL-10-producing CD54RA^- CD4⁺ T cells generated in response to LACK in naive subjects never exposed to Leishmania

Leishmania guyanensis (L.g.)-specific CD8⁺ T cells can be isolated from PBMC of subjects who have never been previously exposed to Leishmania. Cells that produce IFN-γ in response to live L.g. are generated from naive CD45RA⁺ CD8⁺ T cells. The generation of L.g.-specific CD8⁺ T cells requires the presence of whole L.g. or UV-irradiated parasite but not the soluble antigens from L.g. promastigotes. The IFN-γ-producing T cells recognize a specific antigen, the Leishmania homologue of receptors of activated C kinases (LACK) and this antigen but not live L. g. can produce a strong IL-10 response in CD45RA^- CD4⁺ memory T cells from naive subjects. A single epitope (amino acid 156-173) is found to induce the IL-10 synthesis. While the IFN-γ-producing cells are present among CD45RA⁺ CD8⁺ T cells that are CD62L^- CDR7^- and CLA^-, the LACK-reactive IL-10-producing cells are CD4⁺ T cells that are CD62L⁺ CCR7^- and CLA^-.