Lymphocyte binding of aggregated IgG and surface Ig staining in chronic lymphocytic leukaemia

Eleven selected patients with chronic lymphocytic leukemia were evaluated for lymphocyte binding of aggregated IgG and surface Ig staining in order to classify them into B and T cell types. Ten of the 11 patients bound aggregates and stained for surface Ig. In the individual 10 patients the number of cells binding aggregates was high (88-100%, mean 96%) whereas the number staining for surface Ig was more variable (8-100%, mean 62%). Parallel and double labelling experiments with aggregates and sheep red blood cell rosettes, a human T cell marker, provided evidence that aggregates were binding to B cells only, even when surface Ig was not detectable. Aggregates did not bind to human thymocytes. Evidence was presented that lymphocytes from some cases of CLL have low but not absent amounts of surface Ig that may be only partially detected by fluorescence techniques. Aggregate binding appears to be a more sensitive method for the detection of B lymphocytes than surface Ig staining. In one of the 11 patients the leukemic cells were negative in the aggregate binding test. Separate studies on this case also indicated an absence of surface Ig staining and a high percentage of cells forming sheep red blood cell rosettes. It would appear that this case represented a T cell leukemia.