DIFFERENTIAL EXPRESSION OF CD22 (LYB8) ON MURINE B-CELLS

Previous studies have established the distribution, biochemistry and f unctional attributes of human CD22, a B cell-restricted glycoprotein. Recently, molecular cloning of the murine CD22 equivalent revealed thi s molecule to be the same as the previously described Lyb8 alloantigen . Using the anti-Lyb8 mAb Cy34.1.2, the present report documents the e xpression patterns of CD22 within the murine B cell compartment. The r esults demonstrate that in the bone marrow, murine CD22 is absent on t he surface of pro-B cells, pre-B cells and newly emerging IgM(+) B cel ls. CD22 is present at a low density on immature IgM(hi) B cells and f ully expressed on mature recirculating B cells. In the periphery, muri ne CD22 is expressed at mature levels on all B cell subsets including follicular, marginal zone, B1 and switched B cells. Further studies sh owed CD22 to be retained on activated murine B cells for extended peri ods. Finally, in combination with CD23 and heat stable antigen, CD22 c an be used to delineate the immature splenic B cells, and distinguish them from follicular and marginal zone cells. Together, the results de monstrate murine CD22 to be a useful pan marker for all mature B cell subsets.