Two distinct classes of IgG Fc receptors on a human monocyte line (U937) defined by differences in binding of murine IgG subclasses at low ionic strength
Two distinct classes of IgG Fc receptors (FcR) on cells of a human monocytic line (U937) by analyzing the direct binding of murine IgG subclasses in medium of low ionic strength. Four lines of evidence support this contention. (1) The binding of aggregated murine IgB2b (AggmIgG2b) to U937 and Daudi cells was enhanced at low ionic strength, whereas monomeric murine IgG2a (mIgG2a) did not bind to Daudi cells and its high affinity binding to U937 cells was unaffected by changes in ionic strength. (2) Double reciprocal inhibition experiments with U937 cells indicated that the binding of both ligands was inhibited 30 to 135 times more efficiently by the homologous ligand than by the heterologous one. That is, the binding of /sup 125/I-AggmIgG2b was inhibited 50% by 3.5 ..mu..g/ml of AggmIgG2b and 100 ..mu..g/ml of mIgG2a. Similarly, the binding of /sup 125/I-mIgG2a was inhibited 50% by 2.5 ..mu..g/ml of mIgG2a and only 44% by 243 ..mu..g/ml of AggmIgG2b. (3) A monoclonal antibody of the IgG2b subclass raised against an IgG FcR on K562 cells inhibited binding to U937 cells of AggmIgG2b but not of mIgG2a. (4) Trypsinization of U937 cells abrogated by 32% the binding of mIgG2a but did not affect the binding of AggmIgG2b. Human IgG inhibited binding of both AggmIgG2b and mIgG2a t U937 cells. They propose that the newly recognized FcR that binds AggmIgG2b is the human homologue of the murine macrophage IgG2b/1 FcR (FcRII), and that the previously described 72,000 dalton high-affinity FcR on U937 cells that binds mIgG2a is the human equivalent of the murine macrophage IgG2a FcR (FcRI).
- Research Organization:
- Univ. of Rochester Medical Center, NY
- OSTI ID:
- 6845840
- Journal Information:
- J. Immunol.; (United States), Journal Name: J. Immunol.; (United States) Vol. 135:5; ISSN JOIMA
- Country of Publication:
- United States
- Language:
- English
Similar Records
A specific Fc gamma receptor on cultured rat mesangial cells
Human platelet Fc (IgG) receptor and its modulation
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
CELL CULTURES
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GLOBULINS
IMMUNOGLOBULINS
INHIBITION
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
MACROPHAGES
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PHAGOCYTES
PROTEINS
RADIOISOTOPES
RADIORECEPTOR ASSAY
RECEPTORS
SOMATIC CELLS
TRACER TECHNIQUES