The electrophoretic mobility (EM) of peripheral blood lymphocytes from twelve normal subjects and four patients with chronic lymphocytic leukaemia (CLL) was studied in relation to the thymus-derived (T) lymphocytes and bone marrow-derived (B) lymphocytic system. An attempt was made to correlate electrophoretic results with other methods of identifying T and B lymphocytes—T cells by the formation of sheep-cell rosettes and B cells by the formation of erythrocyte–antibody–complement (EAC') rosettes and by staining for surface immunoglobulin. In the normal subjects the majority of cells migrated quickly with a small `tail' of slower cells. It is suggested that the faster populations are T cells and the slower, B. In CLL the majority of the cells were slow migrators. There was agreement between the percentage of fast cells as assessed by electrophoresis with that of T cells by sheep-cell rosetting; there was also some agreement between the percentage of electrophoretically slow cells to B cells by EAC' rosettes or surface immunoglobulin. It was possible to remove some of the B cells by density centrifugation after forming EAC' rosettes. This further defined the T cell peak on electrophoresis. It is concluded that T and B cells carry different surface charge densities which permit them to be separated by electrophoresis and that the malignant B lymphocytes of CLL migrate electrophoretically in a similar fashion to normal B cells. |