Chronic actinic dermatitis. An immunohistochemical study of its T-cell antigenic profile, with comparison to cutaneous T-cell lymphoma.

Chronic actinic dermatitis (CAD) describes a persistent photosensitivity disorder in the absence of continued exposure to photosensitizers; it is characterized by a T-cell infiltrate within the epidermis and dermis. The purpose of this study was to characterize the T-cell infiltrate better immunohistochemically. Serial cryostat sections of fresh-frozen punch biopsy specimens of skin were analyzed in 11 patients with CAD and 3 patients with erythrodermic cutaneous T-cell lymphoma (CTCL). Monoclonal antibodies against the pan T-cell, pan B-cell, and T-cell subsets and the T cell-receptor (TCR) antigens were used. CD8-positive (T-suppressor-cytotoxic) cells were predominant in the epidermis of CAD, while CD4-positive (T-helper) cells were predominant in the epidermis and dermis of CTCL. CDw29-positive (T-memory) cells were predominant in all cases. The number of BF1 (beta-chain constant region of the TCR)-positive cells approximated the number of CD3-positive cells in all CAD cases but was significantly lower than the number of CD3-positive cells in two of three cases of CTCL. There was no clustering or preferential staining with any of the beta-chain variable-region antibodies in any of the specimens. These results indicate that CAD has a characteristic immunophenotype distinct from that of most cases of CTCL and that discordance between BF1 and CD3 expressions did not occur in the CAD cases.