The importance of CD5-positive B cells in nonorgan-specific autoimmune diseases.

CD5, the human counterpart of Ly-1 molecules in the mouse, are detectable but weakly expressed on a minute fraction of circulating B cells. The number of CD5-expressing B cells is increased in patients with rheumatoid arthritis or primary Sjögren's syndrome. These cells are similar to those leading to chronic lymphocytic leukemia (they may be induced to produce multispecific autoantibodies). Multispecific autoantibodies have also been described in the early B cell repertoire.