Bullous pemphigoid (BP), an autoimmune subepidermal-blistering disease of the elderly, is caused by antibodies against BP antigens at the epidermal basement membrane zone (BMZ). CD22 is a B lymphocyte specific response regulator, which is down-regulated after B-cell activation. Old CD22-deficient mice produce class-switched autoantibodies. To assess the role of CD22 in the pathogenesis of BP, we examined CD22 expression on B cells from BP patients and correlated its expression with clinical parameters. B cell expression of CD22 was 20% lower in BP patients when compared to healthy control subjects. In addition, B cells from BP patients showed decreased expression of L-selectin, which is an indicator of leukocyte activation, and CD22 expression levels were correlated with L-selectin expression. These results suggest that the decreased CD22 expression may be associated with the activation of B cells in BP. CD22 expression levels in BP patients did not correlate with the levels of anti-epidermal BMZ antibodies, and old CD22-deficient mice did not develop the anti-epidermal BMZ antibody. These results suggest that a decrease in CD22 expression may not be associated with BP-specific antibody production.