T-lymphocytes and cytokines in sarcoidosis

In the last few years, a number of reports have clearly shown that pulmonary T lymphocytes have evolved a number of effector mechanisms to respond to foreign antigens, ranging from direct cytotoxicity mechanisms to secretion of lymphokines, that have the ability to activate themselves or other pulmonary immunocompetent cells. Furthermore, there is also evidence that lung T cells may have a role in the immunopathogenetic mechanisms taking place in the lung of most immune-mediated diffuse lung disorders. In this paper, we will review the current concepts on the recruitment, homing, and activity of T lymphocytes in the lower respiratory tract of patients with sarcoidosis. The relevant phenotypic and functional abnormalities detected on T cells in sarcoidosis will be discussed. Furthermore, we will comment recent findings on the ability of immunomodulatory molecules, such as proinflammatory cytokines, chemokines, and other cytokines, to regulate T-cell function in immune mechanisms leading to granuloma formation and maintenance.