The detection of membrane-associated complement components (C 3 and C 4) on circulating human normal and leukemic...

Monkey erythrocyte (Mk) rosette formation is described as an exquisitely sensitive method for the detection of complement (C) components on the membrane of human leukocytes. Blocking of the immune adherence receptor on Mk blocked subsequent rosette formation as did pretreatment of leukocytes with antiserum to the C components C 3 and C 4. In vitro C deposition by immune complex formation with normal human lymphocytes enhanced Mk rosette formation, and this could be inhibited with antiserum to C 3. The use of Mk rosette formation revealed that cells from a wide variety of human lymphoid and myeloid leukemias carry membrane-bound C. It was also shown that several lymphoblastoid cell lines, including a T cell line, probably synthesize both C 3 and C 4. Mk rosette formation is not dependent on metabolic activity of the rosetting leukocyte, and it is suggested that this technique will be of value in detecting C deposition in a variety of situations.