Properties of Interleukin-1 and Interferon-γ Receptors in B Lymphoid Cell Line

We have previously shown that interleukin-la (IL-1α) and interferon-γ (IFN-γ) induce surface IgM expression, stimulate Na+/H+exchange, and activate protein kinase C in the murine pre-B lymphocyte cell line, 70Z/3. Because the two structurally different lymphokines induce similar effects, in this study we set out to compare the properties of the IL-1 and IFN-γ surface receptors. In contrast to their similar cellular effects, we found that IL-1α and IFN-γ receptors have different properties. 70Z/3 have high (100 sites/cell) and low (900 sites/cell) affinity IL-1 receptors with dissociation constants (KD) 6 × 10−11and 10−9M, respectively. In contrast, IFN-γ receptors are of one class with a KDof 3 × 10−10Mand are at a higher number, 8000 sites/cell. After binding to their receptors both IL-1α and IFN-γ are internalized and intracellularly degraded, but the rate of internalization of IFN-γ is greater than IL-1α. The effective median concentrations (EC50) of IL-1α- or IFN-γ-induced surface IgM expression are similar (4–5 × 10−12M). However, at this concentration 10-fold more of IFN-γ than IL-1α molecules are bound per cell.