Heterogeneity of type-II interleukin-1 receptors heterogeneity of B-cell interleukin-1 binding created by dimerization of type-II interleukin-1 receptors

Abstract

The binding of IL-1α and IL-1β to two human lymphoblastoid B-cell lines, Raji and RPMI 1788, was compared with binding to the murine T-cell line, EL4. Dramatic differences in IL-1 binding were observed. Both human B-cell lines bound much less IL-1α than IL-1β, expressed 5–10 times more receptors per cell for IL-1β than did the EL4 cell line, and demonstrated a large difference in the ability of IL-1α to compete with IL-1β for binding. The B-cell lines demonstrated a low number of high-affinity IL-1α receptors and a large number of IL-1α receptors with a much lower affinity. Inhibition studies demonstrated that only IL-1β could compete for the binding of radiolabeled IL-1β to the B-cell IL-1R. Furthermore, SDS-PAGE analyses of lysates of the B-cell lines that had been affinity cross-linked with 125I-IL-1α revealed two bands corresponding to IL-1R structures of 60 and 110 kD. These results coupled with a nonequilibrium binding study suggested a dimerization of a common type-II IL-1R polypeptide, the dimer being responsible for the high-affinity IL-1α-binding site of the B-cell lines.