Human platelet Fc receptor for immunoglobulin G. Identification as a 40,000-molecular-weight membrane protein shared by monocytes.
Open Access
- 1 December 1985
- journal article
- research article
- Published by American Society for Clinical Investigation in Journal of Clinical Investigation
- Vol. 76 (6), 2317-2322
- https://doi.org/10.1172/jci112242
Abstract
We have recently shown that human monocytes and U937 cells possess two molecular classes of Fc gamma receptor. One, a 72,000-mol-wt sialoglycoprotein, has high affinity for certain subclasses of human and murine monomeric IgG. The other is a 40,000-mol-wt protein (p40) with low affinity for monomeric IgG but with the capacity to bind IgG aggregates or IgG-coated particles. In the present study, a 40,000-mol-wt single chain protein, apparently identical to p40 from U937 cells, was isolated from surface-radioiodinated human platelets by affinity purification using a murine IgG2b monoclonal antibody to p40. This 40,000-mol-wt protein was not seen when control IgG2b or unrelated murine monoclonal antibodies were employed in place of anti-p40. The same 40,000-mol-wt protein was also recovered from an IgG-Sepharose affinity adsorbent, but not from ovalbumin-or myoglobin-Sepharose. The 72,000-mol-wt Fc gamma receptor of monocytes was not identified on platelets. Monoclonal anti-p40 and Fab fragments derived from this antibody blocked platelet aggregation by heat-aggregated human IgG, whereas a control murine IgG2b protein had little or no inhibitory effect at 500-1,000-fold higher concentrations. A murine IgG1 monoclonal antibody, reactive with an unrelated platelet-specific membrane antigen, did not inhibit platelet responses to aggregated IgG. Anti-p40 did not affect platelet aggregation by thrombin, collagen, or fibrinogen plus ADP. Although anti-p40 did not directly aggregate platelets in the concentrations employed, cross-linking with F(ab')2 goat anti-murine Ig induced apyrase-sensitive aggregation of anti-p40-treated platelets. This indicates that p40 possesses transmembrane linkage for platelet activation and secretion. These observations strongly suggest that this newly recognized 40,000-mol-wt platelet membrane protein serves as an Fc gamma receptor.This publication has 27 references indexed in Scilit:
- 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.The Journal of Immunology, 1985
- Enhancement of platelet response to immune complexes and IgG aggregates by lipid A-rich bacterial lipopolysaccharides.The Journal of Experimental Medicine, 1978
- Receptors for IgG: subclass specificity of receptors on different mouse cell types and the definition of two distinct receptors on a macrophage cell line.The Journal of Experimental Medicine, 1977
- HEREDITARY C5 DEFICIENCY IN MAN .3. STUDIES OF HEMOSTASIS AND PLATELET RESPONSES TO ZYMOSAN1977
- Human platelet-initiated formation and uptake of the C5-9 complex of human complement.Journal of Clinical Investigation, 1976
- Pneumococcus-induced serotonin release from human platelets. Identification of the participating plasma/serum factor as immunoglobulin.Journal of Clinical Investigation, 1975
- Continuous cultures of fused cells secreting antibody of predefined specificityNature, 1975
- Release of Serotonin from Human Platelets Induced by Aggregated Immunoglobulins of Different Classes and SubclassesJournal of Clinical Investigation, 1973
- Platelet Fc Receptor as a Mechanism for Ag-Ab Complex-induced Platelet InjuryThrombosis and Haemostasis, 1973
- Immune reactions of human blood platelets. I. A comparative study on the effects on platelets of heterologous antiplatet antiserum, antigen-antibody complexes, aggregated gammaglobulin and thrombin.1968