SPECIES SPECIFICITY IN THE BINDING OF IGG TO MACROPHAGES

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 37  (4) , 835-840
Abstract
The binding of human Ig[immunoglobulin]G1 and IgG3 and rabbit IgG to guinea pig peritoneal macrophages was examined, and differences between the species, in terms of their binding mechanisms, were characterized. Rabbit IgG bound with high affinity (Kass = 3.11 .+-. 0.45 .times. 106 M-1) to a finite number of receptor sites per cell (1.26 .+-. 0.29 .times. 106) and competitively inhibited the binding of guinea pig IgG2. Heterogeneity in binding, with distinct high and low affinity components, was observed when human IgG3 was reacted with guinea pig macrophages, while human IgG1 exhibited only low affinity binding. Neither human IgG subclass competed effectively with guinea pig IgG2 for its cell receptor. Rabbit IgG appeared to cross-react with a macrophage receptor for guinea pig Ig, whereas the human IgG subclasses bound to macrophage membrane components that remained undefined.