Release and reconstitution of Fc receptors from normal human mononuclear cells.

Nylon-fibre non-adherent cells isolated from human peripheral blood, release their Fc receptors for IgG upon culture in vitro in medium containing 0-2% foetal calf serum. The majority of Fc+ nylon-fibre non-adherent cells was reconstituted using supernates from different cell populations of human peripheral blood. The best reconstituting activity was detected in the supernates from glass-adherent cells, or unfractionated Lymphoprep cells, while those obtained from nylon-fibre non-adherent cells gave variable results sometimes containing no activity at all. It was shown that reconstitution was achieved by the uptake of Fc receptors present in the supernate which inhibited Fc rosette formation. Inhibition was also achieved with supernates from peripheral blood cells of a patient with monocytic leukaemia. Only autologous but not allogeneic cell supernates could reconstitute Fc receptors. This suggests that the reconstitution of Fc receptors on peripheral blood Fc-IgG lymphocytes by monocytic cells is under genetic control.