LEISHMANIA-MAJOR-SPECIFIC, CD4-II-RESTRICTED T-CELLS DERIVED INVITRO FROM LYMPHOID-TISSUES OF NAIVE MICE(, MAJOR HISTOCOMPATIBILITY COMPLEXCLASS)

Several studies indicate that the outcome of experimental murine cutan eous leishmaniasis caused by Leishmania major (Lm) is determined by im munological events occurring shortly after infection. These events lea d to outgrowth of either protective CD4+ T cells in the C57BL/6 mouse, which cures, or exacerbative cells in the BALB/c mouse, which succumb s to disease. Potential factors influencing the outgrowth of protectiv e or exacerbative T cells include antigen-presenting cells (APC), cyto kines, and parasite antigens. An in vitro system, in which one could p recisely control the factors shaping early events in the T cell respon se to Lm, would be very useful. To this end, we have examined the in v itro response of naive lymphocytes to Lm promastigotes. The data prese nted here show that Lm-specific CD4+ T cell receptor alpha/beta+ T cel ls can be generated in vitro from spleen and lymph node cell populatio ns of naive mice. Furthermore, they can be obtained from the CD44low ( unprimed) population of T lymphocytes, indicating that in vitro primin g occurs. The ability to generate these T cells is dependent on the pr esence of live parasites and is not due to a parasite-derived nonspeci fic T cell mitogen. Restimulation, as assayed by proliferation, requir es APC bearing syngeneic I-A. Optimal restimulation of the in vitro de rived T cells is achieved only when live promastigotes are used. The T cells do not proliferate in response to a frozen-and-thawed lysate of promastigotes, yet they exhibit mild reactivity to lysates prepared f rom heat-shocked promastigotes. Furthermore, they do not recognize two predominant antigens on the promastigote surface, lipophosphoglycan a nd gp63. T cells derived in vitro with Lm show crossreactivity with li ve L. donovani, less crossreactivity with live L. mexicana, and no cro ssreactivity with live Bacillus-Calmette-Guerin or live Brugia malayi microfilariae. Finally, these early T cells, whether derived from heal ing C57BL/6 or nonhealing BALB/c mice, produce interleukin 2 (IL-2), I L-4, and interferon gamma.