Spontaneous mouse erythrocyte-rosette formation: correlation with surface immunoglobulin phenotype in hairy-cell leukaemia.

Mouse-rosette formation was investigated in a variety of leukaemias and lymphomas, and it was found that this phenomenon was restricted to the B lymphocytes of chronic lymphocytic leukaemia and hairy-cell leukaemia. Eighteen of nineteen cases of chronic lymphocytic leukaemia expressed the mouse receptor, but only eight of fifteen cases of hairy-cell leukaemia showed significant mouse rosette formation by peripheral blood cells. A much higher percentage of splenic hairy cells, compared with peripheral blood cells, formed mouse rosettes, but receptor expression was found to be dependent on the surface immunoglobulin (SIg) phenotype. Cases forming mouse rosettes had multiple heavy chain isotypes including IgD on the surface, but the ontogenically more mature SIgG-only cells from other cases failed to form rosettes, whether from peripheral blood or spleen. Cultured hairy cells lost the ability to form mouse rosettes, and receptor expression by peripheral blood hairy cells fluctuated widely in the days following splenectomy. The results suggest that the mouse erythrocyte receptor is an early marker in B cell differentiation and that receptor expression by individual cells may depend on the age of the cell.