Immune reactivity to fractionated Leishmania aethiopica antigens during active human infection

Fractionated antigen preparations of Leishmania aethiopica parasites were used to stimulate the peripheral blood lymphocytes of patients with active cutaneous leishmaniasis. In assays measuring lymphocyte proliferation, 9 of 10 patients with similar clinical presentations of infection responded in a similar pattern to the fractionated antigens. Marked proliferation was observed in response to antigen fractions with molecular masses of 43 to 36, 33 to 27, and less than 22 kDa. The induction of relatively high levels of gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) was also observed in responses to these same three antigen fractions. In contrast, the proliferative, IFN-γ, and TNF-α responses of patient lymphocytes to antigens with a molecular mass greater than 60 kDa were uniformly low. The results of this study suggest that the antigens of Leishmania parasites, which are recognized by T cells in patients with active cutaneous leishmaniasis, may be partitioned in the lower-molecular-mass antigenic determinants associated with whole-parasite preparations. The observed association between antigen-induced proliferation and IFN-γ and TNF-α production may be indicative of potential disease-limiting immune effector activities which have developed during infection.