Functional aspects of T cell diversity in visceral leishmaniasis.

Co-ordination between innate and adaptive immunity is a foremost crucial immunological interactions. The interaction is beneficial for the survival of the host against infectious agent and also detrimental for the pathogen during their future encounter. Major cellular components to bridge the gap of innate and adaptive immune system include B cells, varieties of T cell subsets and their interaction with antigen presenting cells. T cells are the components of immune system which recognise antigen that are specifically presented with the different class of MHC molecules like MHCI and MHCII marking the diversity of exogenous and endogenous nature of antigen. T cells further differentiate in varieties of morphological and immunological forms like CD4+, CD8+ T cells, Th-17, Treg and γδ-T cells based on the nature of antigen, interaction and polarizing factors. Therefore the evolutionary selections of these diversities have a different functional aspect which is not only dependent upon their percentage presence but more promisingly dependent upon their physiological state and local environment. Thus this review is highlighting the major contributions of T cells subsets using an infectious disease model of visceral leishmaniasis and also helpful in explaining the reason for the non-responsiveness of the T cells subsets during the onset and progression of infection.