Receptor Sites for Complement on Certain Human Peripheral Blood Lymphocytes

Abstract Receptor sites for complement (C) on human peripheral blood lymphocytes were assessed by their capacity to bind red cells coated with C. Rosette formation was observed around 20% (12 to 29%) of blood lymphocytes obtained from normal donors. The number of lymphocytes with rosettes was related to the amount of C bound to the red cells. Treatment of lymphocytes with trypsin or incubation with antilymphocyte globulin inhibited the receptor activity. In contrast to the inhibition of rosette formation resulting from adding EDTA to the incubation mixture of monocytes and C-coated red cells, there was no inhibitory effect by EDTA on lymphocytes and C-coated red cells. Rosettes were almost exclusively observed around small lymphocytes. When lymphocytes were separated in a discontinuous bovine serum albumin gradient, the highest percentage of lymphocytes with receptor activity was found in fractions of low density. In patients with chronic lymphocytic leukemia there was a significantly lower percentage of rosette-forming cells.