Interactions between microglia and T cells in multiple sclerosis pathobiology

Brain-resident microglia and T lymphocytes recruited into the central nervous system both play important roles in the neuropathology of multiple sclerosis. The microglia and recruited T cells are in close proximity in lesions of multiple sclerosis and in animal models, suggesting their potential for interactions. In support, microglia and T cells express a number of molecules that permit their engagement. Here we describe the interactions between T cells and microglia and the myriad responses that can result. These interactions include antigen presentation by microglia to activate T cells, the T cell activation of microglia, their progressive stimulation of one another, and the production of injurious or neurotrophic outcomes in their vicinity. Important considerations for the future include the nature of the T helper cell subsets and the M1 and M2 polarized nature of microglia, as the interactions between different subsets likely result in particular functions and outcomes. That T cells and microglia are in proximity and that they interact in lesions in the central nervous system implicate them as modifiers of pathobiology in multiple sclerosis.