Characterization of chronic lymphocytic leukemia (CLL) cells with low density of surface membrane bound immunoglobulins (smIg).

The study consists of 6 CLL patients with leukemic blood lymphocytes lacking T-cell characteristics and with smIg on only a very small fraction of the cells detected by microscopy or FACS analysis after direct immunofluorescence (IFL) staining. Using B-cell specific monoclonal antibodies all leukemias were found to be of the B-cell type. SmIg, mainly of IgD-class and the monotypic light chain, was detected on a large number of cells in all cases when using direct IFL. No lymphocyte clone was judged to be of the pre-B-cell type or represented fully differentiated terminal B-cells. CLL cells from the individual cases probably represent intermediate B-cell maturation steps. The results lend no support to the suggestion that this subtype of CLL necessarily belongs to an early stage of differentiation just beyond the pre-B-cell level.