CD7-NEGATIVE HELPER T-CELLS ACCUMULATE IN INFLAMMATORY SKIN-LESIONS

Recently, we identified a articular T-cell subset in the peripheral bl ood of normal individuals that lack CD7 expression. In this study we d etermined the portion of CD7- T cells in the peripheral blood and skin of patients with various inflammatory skin diseases. We found that sk in-infiltrating lymphocytes isolated from different benign and maligna nt skin lesions (n = 20) contain a high portion of CD7- helper T cells , whereas the number of CD7- T cells in the peripheral blood was not a ltered compared to healthy controls. Cell activation in vitro did not induce CD7 expression in negative T cells but increased CD7 expression in CD7-positive cells. Thus, lack of CD7 expression seems to be a sta ble characteristic in a major subset of skin-infiltrating lymphocytes. During long-term culture of CD7- helper T-cell clones derived from a psoriasis skin lesion, no phenotypic change in the CD7 phenotype could be monitored by sequential flow-cytometric analyses. No CD7 mRNA coul d be detected by Northern blot analysis, indicating transcriptional re gulation of CD7 expression. The results show that CD7- T cells accumul ate in certain inflammatory skin lesions without alteration of the cir culating CD7- population. These cells may be identical to or derived f rom CD7- T cells of the peripheral blood.