Differential expression of CD22 (Lyb8) on murine B cells

Previous studies have established the distribution, biochemistryand functional attributes of human CD22, a B cell-restrictedglycoprotein. Recently, molecular cloning of the murine CD22equivalent revealed this molecule to be the same as the previouslydescribed Lyb8 alloantigen. Using the anti-Lyb8 mAb Cy34.1.2,the present report documents the expression patterns of CD22within the murine B cell compartment. The results demonstratethat in the bone marrow, murine CD22 is absent on the surfaceof pro-B cells, pre-B cells and newly emerging lgM⁺ B cells.CD22 is present at a low density on immature IgM^hi B cells andfully expressed on mature recirculating B cells. In the periphery,murine CD22 is expressed at mature levels on all B cell subsetsincluding follicular, marginal zone, B1 and switched B cells.Further studies showed CD22 to be retained on activated murineB cells for extended periods. Finally, in combination with CD23and heat stable antigen, CD22 can be used to delineate the immaturesplenic B cells, and distinguish them from follicular and marginalzone cells. Together, the results demonstrate murine CD22 tobe a useful pan marker for all mature B cell subsets.