Experimentally induced cutaneous leishmaniasis: are L3T4+ T cells that promote parasite growth distinct from those mediating resistance?

A considerable body of evidence from various laboratories indicates that specific T cell responses generated during infection with Leishmania parasites play an important role both in the resolution and progression of cutaneous leishmaniasis. Recent data, summarized in this article, indicate that resolution of lesions and promotion of disease not only result from the activity of functionally distinct parasite-specific L3T4+ T cells but could also be mediated by functionally similar L3T4+ T cells differing only in their fine antigenic specificity. This contention is based on observations which suggests that (a) the induction of T cell tolerance to parasite antigens present during the early phase of infection is beneficial to the host, and (b) the specificity of L3T4+ T cell lines and clones capable of exacerbating the development of lesions is different from that of T cells mediating protection.