Acquisition of cell-mediated immunity to Leishmania. I. Primary T-cell activation detected by IL-2 receptor expression.

In order to analyse the early stages of the T-cell response to Leishmania, bioassays for detecting low levels of IL-2 receptor expression both in bulk culture and under limiting dilution conditions have been used. Infection of C57BL/10 mice with Leishmania donovani amastigotes leads to the appearance of antigen-specific T lymphocytes bearing high-affinity IL-2 receptors 24-72 hr later. Phenotypic analysis by complement-mediated cytotoxicity indicates that these activated T cells comprise both L3T4+, Lyt2- and L3T4-, Lyt2+ populations. The data also suggest the existence of activated cells bearing both these markers. By both assay techniques, the appearance of receptor-positive populations appears transitory, with few such cells detectable at 7 days post-infection. The implications of these data for further studies of murine leishmaniasis are discussed.