Fc receptor bearing 'hairy cells' of leukaemic reticuloendotheliosis bind soluble antigen--antibody complexes and adhere to immobilized complexes, but fail to mediate antibody dependent cellular cytotoxicity.

The majority of hairy cells from three patients with leukaemic reticuloendotheliosis were adherent cells bearing surface immunoglobulin, complement receptors, and Fc receptors. Highly purified populations of malignant hairy cells, which readily bound soluble antigen-antibody complexes in suspension and were able to adhere to immobilized antigen-antibody complexes, were examined for their ability to mediate ADCC. Two patients with greater than 90% FcR positive cells failed to mediate ADCC. When initially examined, a third patient, with fewer malignant cells, demonstrated a less marked impairment of cytolysis. When reexamined at a later date, this patient had an increased number of hairy cells and concomitantly demonstrated more impaired ADCC effector cell activity. Absorption of surface immunoglobulin bearing cells onto plastic surfaces coated with goat anti-human immunoglobulin resulted in a complete depletion of FcR, sIg positive, hairy cells. The remaining nonadherent fraction, containing 5.5% FcR positive, sIg negative cells, was able to mediate ADCC as effectively as the normal controls. These results indicate that although FcR bearing hairy cells readily bind soluble antigen-antibody complexes and adhere to immobilized complexes, they were unable to mediate ADCC.