Susceptibility to murine cutaneous leishmaniasis correlates with the capacity to generate interleukin 3 in response to leishmania antigen in vitro.

Spleen cells from genetically susceptible BALB/c mice infected with Leishmania major produced higher levels of IL-3 in response to leishmania antigens or concanavalin-A in vitro compared to that of genetically resistant CBA mice throughout the course of infection. The capacity to generate IL-3 in BALB/c mice increased with disease progression. The correlation between susceptibility to L. major infection and the capacity of spleen cells to produce IL-3 also extends to other mouse strains. Thus genetically highly resistant CBA and Biozzi Low mice are low IL-3 producers, whereas the highly susceptible BALB/c and Biozzi High mice are high IL-3 producers. The resistant C57BL/10 and C3H mice produce intermediate levels of IL-3. BALB/c mice recovered from L. major infection following a sublethal dose of gamma-irradiation are refractory to further infection. The capacity of the spleen cells from these cured mice to produce IL-3 upon a challenge infection was similar to those of the resistant CBA mice. The IL-3 generated by activated T cells was measured by IL-3 dependent cell lines, 32D and FDC-P2. The spleen cells from infected BALB/c mice also contain a population of IL-3 responding cells whose number increases as disease progresses. A similar population of IL-3 responding cells was barely detectable in the resistant CBA mice or BALB/c mice rendered immune by prior gamma-irradiation. These results therefore demonstrate a direct correlation between the susceptibility to L. major infection and the capacity of splenic T cells from infected mice to produce a continuous elevated level of IL-3. The possible role of IL-3 in the immune regulation of cutaneous leishmaniasis is discussed.