IFNγ-producing, virus-specific CD8+ effector cells acquire the ability to produce IL-10 as a result of entry into the infected lung environment

It has become clear that T cells with the potential to negatively regulate the immune response are normal constituents of the immune system. These cells often mediate their effects through the production of immunosuppressive factors. At present our understanding of how these cells are generated is limited. Here we report the presence of a population of IL-10-producing, virus-specific CD8+ T cells in the lungs of mice following acute respiratory infection. These cells were only found at minimal levels in the spleen and draining lymph node; instead they were restricted primarily to the infected lung tissue. A major finding from this study is demonstration that the ability to produce IL-10 can be acquired by IFNγ-producing effector cells following entry into the infected lung. These studies suggest IL-10 production is the result of further differentiation of an antigen-specific CD8+ T cell that is governed by signals present in infected lung tissue.