Cutaneous T-cell lymphomas: clues of a skin-thymus interaction.

The common cellular denominator of the neoplastic lymphocytes of the cutaneous lymphomas is the presence of membrane markers of T-cell identity. For this reason these disorders are grouped together as "cutaneous T cell lymphomas". These neoplastic T-cells have a characteristic tissue distribution (preferentially infiltrating the skin and sparing the bone marrow). The abnormal T-cells of the leukemic phase of these disorders produce large amounts of macrophage migration inhibitory factor, which may adversely affect macrophage mobilization, and also stimulate differentiation of B-cells into plasma cells. The antigenic properties, the usual slow rate of replication, and the circulatory route of these cells may be exploitable in the development of more specific therapeutic approaches to the management of affected patients. Although these T-cells have an affinity for the skin, the role of this organ in the proliferation and differentiation of these cells is as yet not established. Localization of the primary site(s) of proliferation awaits completion of in vivo kinetic studies. The neoplastic T-cells from such patients provide important cellular reagents for the study of diverse aspects of lymphocyte biology. They have already been used to investigate mechanisms of lymphocyte triggering, isolate histocompatibility antigens, and characterize anti-T-cell immunoglobulin from patients with systemic lupus erythematosus.