In contrast to FcRn the soluble Fc receptor (FcRI) of human peripheral mononuclear blood cells (PMBC) is shed from PMBC following a 4-37°C temperature shift and inhibits rosette formation of nonshed PMBC with antibody-coated erythrocytes (EA). Purified FcRI could be polymerized by tissue transglutaminase as was revealed by SDS-polyacrylamide gel electrophoresis. Comparing the Sephadex G150 elution profile of the EA rosette inhibitory capacity of FcRI vs FcRI incubated in the presence of transglutaminase, the latter was found in a higher mol. wt region and could inhibit rosette formation by both FcRI and FcRII. Furthermore, the shedding of FcRI could be prevented by the addition of transglutaminase or Ca2+-ionophore A23187 (which leads to the activation of PMBC transglutaminase) to the cell suspension. The function of FcRII was not affected by either the addition of transglutaminase or Ca2+ionophore to the cells. The results point to the involvement of transglutaminase in the determination of the functional state of the Fc receptor on the cell surface.
ASJC Scopus subject areas
- Molecular Biology