Mouse RBC rosettes in chronic lymphocytic leukaemia: different expression in blood and tissues

Mouse RBC (M) rosettes were investigated on lymphocytes from peripheral blood (PB) and various tissues in twenty patients with chronic lymphocytic leukaemia and one with follicular lymphoma. In all cases studied, the percentage of M rosettes was significantly higher in PB (median 64%) than in bone marrow (median 15%) and lymph node (median 12%). These differences were statistically significant (P less than 0.01). The possibility that these differences were related to technical factors was ruled out by a number of control procedures. It is suggested that the different expression of M rosette formation reflects the property which determines whether a lymphocyte enters the peripheral blood or remains fixed in the tissues.