Changes of Fcγ Receptor-Related Properties Induced by Interaction of Human Lymphocytes with Insoluble Immune Complexes

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Abstract
An in vitro model was designed to investigate the fate of membrane receptors for Fcγ (FcγR) on human lymphocytes after a first interaction with antigen-antibody complexes or aggregated immunoglobulins. After the binding of erythrocyte-antibody (EA) complexes to FcγR, a process of dissociation occurs. It is temperature dependent and faster at 37°C than at 4°C. In addition, the dissociation becomes progressively irreversible as shown by the inability of dissociated cells to reform EA rosettes or to act as effectors in antibody-dependent cell cytotoxicity. Similarly, inhibition of EA rosette formation by aggregated human IgG could be reversed by trypsinization after incubation at 4°C but not at 37°C. Several mechanisms that might have accounted for the irreversible dissociation of EA rosettes could be excluded: no antibody fragments could be evidenced at the cell surface, trypsinization did not restore the capacity to form EA rosettes, and lymphocytes were shown to be alive, to incorporate amino acids, and to release β2 microglobulin. The phenomenon was therefore termed modulation of FcγR. Finally, FcγR was not detectable at the cell surface after culture for up to 3 days, suggesting that FcγR was rapidly shed and/or slowly resynthetized after modulation.

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