FC-RECEPTORS OF A HUMAN PROMYELOCYTIC LEUKEMIC-CELL LINE - EVIDENCE FOR 2 TYPES OF RECEPTORS DEFINED BY BINDING OF THE STAPHYLOCOCCAL PROTEIN A-IGG1 COMPLEX

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 125  (1) , 448-453
Abstract
Specificity and kinetics of binding of purified monomeric human and murine myeloma immunoglobulins (Ig) to Fc receptors were studied in a human promyelocytic cell line (HL-60). HL-60 cells contain approximately 20,000 Fc receptors/cell and bind human IgG1, IgG3 and mouse IgG2a with high affinity (Kd 5-10 nM). Kinetic studies of the binding of IgG1 to HL-60 cells demonstrate rapid exchange with ambient Ig with approximately 1/2 of the surface-bound IgG1 exchanging every 25-30 min at 37.degree. C. Estimation of the equilibrium binding constant from the rates of association and dissociation of IgG1 agrees well with the values obtained from Scatchard analysis of equilibrium binding of radioiodinated IgG1. Approximately 1/2 of the Fc receptors of HL-60 cells can bind IgG1 complexed to protein A. This result was independent of the concentration of protein A (0.5-200 .mu.M) or the time of incubation of IgG1 with protein A. When protein A was incubated with HL-60 cells at 37.degree. C and rapidly washed at 0.degree. C, protein A apparently did not degrade Fc receptors or interact with the Fc receptor sites on HL-60 cells. The complexes formed between protein A and IgG1 sedimented at 7-9S by ultracentrifugation. There may be 2 types of Fc receptors on HL-60 cells which can be distinguished by their ability to bind the IgG1-protein A complex.

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