Role of T cell subsets during the recall of immunologic memory to Leishmania major.

The contributions of different T cell subpopulations to the maintenance of immunity during secondary Leishmania major infections were analyzed in healed, resistant animals by depletion of T cell subsets in vivo. The strong delayed-type hypersensitivity mounted in immune genetically resistant mice upon challenge with viable promastigotes was mediated by both CD4+ and CD8+ T cells. Each T cell subpopulation alone contributes, although to a different extent, to the resolution of secondary lesions; both subsets, however, are required for an efficient and rapid healing of the secondary lesions and the decrease in the parasite burden in infected tissues. The results indicate that in immune, genetically resistant CBA mice, the activity of both T cell subsets is required for successful resistance to reinfection and an efficient maintenance of immunity.