Leishmania donovani-reactive Th1- and Th2-like T-cell clones from individuals who have recovered from visceral leishmaniasis
Infection and Immunity, Volume 61, No. 3, Year 1993
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Infections in humans by Leishmania donovani parasites can result in a fatal disease, visceral leishmaniasis (VL), or in a self-limiting asymptomatic infection. In murine models of the infection employing Leishmania major, the course of the disease can be directed into a VL-like syndrome by interleukin-4 (IL-4)-producing Th2 cells, or cure may result by Th1 cells secreting gamma interferon (IFN-γ). The present study examined the potential of human T cells to generate Th1 or Th2 responses to L. donovani. The profiles of IFN-γ, IL-4, and lymphotoxin secretion after antigen stimulation were analyzed in a panel of L. donovani-reactive CD4+ human T- cell clones generated from individuals who had recovered from VL after antimonial treatment. Two of the T-cell clones produced large amounts of IL- 4 without production of IFN-γ, seven clones produced both IFN-γ and IL-4, and eight produced only IFN-γ. This is the first report of a Th1- and Th2- type response in human leishmaniasis. These results suggest that in analogy with murine models, there is a dichotomy in the human T-cell response to L. donovani infections. Preferential activation of IL-4-producing Th2-like cells may be involved in the exacerbation of human VL, whereas activation of IFN- γ-producing Th1 cells may protect the host from severe disease. Identification of leishmanial antigens activating one or the other type of T cells will be important in the development of vaccines against leishmaniasis.