Monocyte Fc gamma receptor recognition of cell-bound and aggregated IgG
F Gomez, P Chien, M King, P McDermott, AI Levinson, MD Rossman and AD Schreiber
University of Pennsylvania Cancer Center, Philadelphia 19104.
Monocyte and macrophage Fc gamma receptors are important components in the
recognition of IgG-coated cells and IgG-containing immune complexes. Two
proteins have been identified on human peripheral blood monocytes that can
function as Fc gamma receptors, Fc gamma RI (70 Kd) and Fc gamma RII (40
Kd). We studied the role of Fc gamma RI and Fc gamma RII on human monocytes
by examining their binding of IgG- sensitized cells (human IgG
anti-D-coated RBCs and rabbit IgG- sensitized sheep RBCs) and their binding
of human trimeric IgG. To examine the function of monocyte Fc gamma RII, we
used an anti-Fc gamma RII monoclonal antibody (MoAb) that competes for the
Fc gamma RII ligand binding site. Preincubation of monocytes with
saturating concentrations of anti-Fc gamma RII MoAb did not alter the
recognition of IgG (anti-D)-sensitized human RBCs by monocytes.
Furthermore, ligand- binding studies demonstrated that anti-Fc gamma RII
antibody altered neither the number nor the affinity of monocyte-binding
sites for human IgG trimer. Anti-Fc gamma RII inhibited monocyte binding of
rabbit IgG- sensitized sheep RBCs, but only at low ionic strength or
temperature when increased numbers of monocyte Fc gamma RII were expressed.
At low ionic strength and 4 degrees C, anti-Fc gamma RII also partially
inhibited monocyte binding of human trimeric IgG. Thus, monocyte Fc gamma
RII does not appear to recognize IgG-sensitized RBCs or trimeric IgG at
physiologic temperatures and ionic strength. The data suggest that Fc gamma
RI is the primary Fc gamma receptor on monocytes involved in the binding of
IgG (anti-D)-sensitized erythrocytes and low mol wt complexes of IgG.
Volume 74,
Issue 3,
pp. 1058-1065,
08/15/1989
Copyright © 1989 by The American Society of Hematology
