Serum‐induced suppression of interferon (IFN) activity. Lack of evidence for the presence of specific autoantibodies to IFN‐α in normal human sera
IgG antibodies binding to different IFN species have been described in sera of healthy and diseased individuals. Human serum immunoglobulins have also been shown to interfere with IFN bioactivity. To characterize these antibodies, human recombinant IFN‐α2A (rIEN‐α) was radioiodinated, and ligand binding studies were performed in human sera as well as on the human cell line A‐549 in the presence of human serum. 125I‐rIFN‐α bound to serum factors of healthy individuals. However, less than 3% of the binding was to IgG and the binding was non‐saturable and therefore most likely non‐specific. 125I‐rIFN‐α bound to receptors on A‐549 cells, and the ligand‐receptor complexes appeared to internalize. However, both cell binding and internalization of 125I‐rIFN‐α were independent of the presence of human serum. We conclude that normal human sera do not contain detectable autoantibodies to rIFN‐α.