In this investigation of B cells expressing the CD5 (Leu-1) cell surface marker, we found increased numbers of these cells in 13 of 19 patients with primary Sjiigren's syndrome (SS) (68%), as well as in the rheumatoid arthritis patients. The percentage of B cells that demonstrated increased expression of CD5 was 46% in SS patients, 47% in rheumatoid arthritis patients, 24% in systemic lupus erythematosus patients, and 26% in normal subjects. Over a 2-year period, CD5 expression on B cells was a stable finding in several patients, except for 2 who required either steroid therapy or combined chemotherapy and irradiation for malignant lymphoma. Both of these patients had clinical remissions and their levels of CD5+ B cells returned to normal. The first patient had a clinical picture of SS/systemic lupus erythematosus overlap, associated with polyclonal B cell activation and decreased production of interleukin-2 in response to stimulation with phytohemagglutinin. These cellular immune abnormalities returned to normal after the institution of corticosteroids. Our observations suggest a rela-

We studied the expression and function of 2 cell surface markers that induce T cell activation, CD3 and CD5, in 19 patients with primary Sjogren's syndrome (SS). The expression of CD3+ lymphocytes was normal, but CD3 function was moderately reduced, as measured by anti-CD3-induced T cell proliferation. Anti-CD3-induced stimulation of T cell help for Ig production and non-major histocompatibility complex-restricted (natural) killing were normal. In contrast, there was reduced expression and function of the CD5 molecule on peripheral blood lymphocytes of the SS patients. The ratio of CD5+ to CD3+ lymphocytes was 0.45 in SS patients compared with 0.85 in normal subjects, indicating that the CD3+ cells are relatively CD5-deficient in SS patients. Anti-CD5 monoclonal antibody did not augment suboptimal anti-CD3 stimulation of whole peripheral blood lymphocytes or of purified T lymphocytes from SS patients, which indicated impaired functioning of the CD5 molecule. A significant impairment in proliferation was found in response to phorbol myristate acetate and to ionomycin in combination, suggesting

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