SKIN-SELECTIVE LYMPHOCYTE HOMING MECHANISMS IN THE PATHOGENESIS OF LEUKEMIC CUTANEOUS T-CELL LYMPHOMA

The concept of skin-associated lymphoid tissue embraces those cells an d functions that are integrated in the cutaneous host defense. Recentl y, it has been possible to identify those circulating T-cells that are skin associated. These cells display the cell-surface phenotype of me mory T tells (CD45RO+) and express the cutaneous lymphocyte antigen, a tissue-selective homing receptor involved in directing T-cell traffic to inflamed skin. To investigate the participation of this skin-assoc iated T-cell subset in the pathogenesis of cutaneous T-cell lymphoma, we studied 16 patients with erythrodermic cutaneous T-cell lymphoma fo r the presence of these surface proteins on circulating cells. Results were compared with eight patients in remission and eight with minimal patch-plaque cutaneous T-cell lymphoma. The mean expression of both C D45RO and cutaneous lymphocyte antigen were significantly greater in t he erythrodermic patients than in the other two patient groups. Expres sion of these markers was shown to be on the cells of the malignant cl one by two-color flow cytometry. These results demonstrate that the ma lignant cells of cutaneous T-cell lymphoma express the markers of skin homing lymphocytes and that their levels are increased in the erythro dermic cutaneous T-cell lymphoma patients. Moreover, the findings sugg est a critical role for the skin-selective homing receptor cutaneous l ymphocyte antigen in the pathogenesis of cutaneous T-cell lymphoma.