Role of T Cells in Leishmania Infection
Chiranjib Pal and Sunil Martin
from: Leishmania: Current Biology and Control (Edited by: Subrata Adak and Rupak Datta). Caister Academic Press, U.K. (2015) Pages: 147-166.
In Leishmaniasis, Th1-related cytokines production seems to be crucial for host control of parasite burden and clinical cure. Visceral and diffuse cutaneous Leishmaniasis are characterized by negative skin test for parasite antigens and failure to produce Th1 cytokines, whereas tegumentary leishmaniasis is characterized by positive skin test and the ability of peripheral blood mononuclear cells (PBMCs) to produce IL-12 and IFN-γ (Th1 cytokine). As a matter of fact, IL-4 and IL-13 (Th2 cytokines) promote disease progression in cutaneous Leishmaniasis, whereas IL-4 seems to enhance protective type-1 responses in visceral Leishmaniasis. Thus, immune response to intracellular parasites should dismiss the Th1/Th2 paradigm of resistance/susceptibility, embracing theory of a more biologically relevant network of regulatory/ counter regulatory interactions. Moreover, the presence of antigen specific regulatory T cell subsets may provide an environment that contributes to the balance between Th1 and Th2 cells. Finally, the involvement of CD8+ T cells has been described, but the modality of their role and function, in this kind of infection, has not been expanded so far. Recently discovered Th17, Th9 and Tfh subsets and related cytokines have been reported to perform diverse functions in the course of Leishmaniasis as a whole. Leishmania is one of the first microbes credited to employ T-reg cells for immunoevasion. IL-10 producing Foxp3+ and Foxp3- T-reg subtype perpetuate immunosuppression whereas inflammatory CD8+T cells counter the immunosuppression forcing the parasite to metastasize. Detailed understanding of this immune-regulatory check points may expose novel drug targets which may help in developing therapies against diseases with parallels molecular etiology read more ...