Defective function of T lymphocytes in psoriasis.

The distribution of thymus-derived (T) and bone marrow-derived (B) lymphocytes in 100 patients with psoriasis were studied by the rosetting techniques. Depression of the number of T lymphocytes forming spontaneous rosettes with sheep erythrocytes (E rosettes) occurred in 66% of patients, whereas no difference in B lymphocytes bearing C3 receptor (EAC rosettes) was observed between psoriatics and normals. The decrease in E rosettes was associated with the active phase of the disease. This disappeared 4-6 wk after onset of remission, which suggested that the abnormality in T-cell marker distribution is transitional. Lymphocytes forming neither E nor EAC rosettes, which were found to be significantly increased in active psoriasis, were identified as T lymphocytes since they reacquired normal E rosette function during short-term preincubation with concanavalin A (Con A). A serum factor was also demonstrated which inhibited E rosette formation by normal peripheral blood lymphocytes. Its activity increased linearly within 2 mo from the onset of skin lesions. The data suggest that in active psoriasis serum factors may be coated on the lymphocyte surface membrane which may be responsible for blocking of specific receptor for sheep erythrocytes and/or interfere with T lymphocyte function.