Renal deposition of alpha interferon in systemic lupus erythematosus

Earlier studies from several laboratories showed that interferon-alpha (IFN-alpha) is present in the sera of a large percentage of patients with systemic lupus erythematosus (SLE). We now report the detection of IFN-alpha by indirect immunofluorescence in renal sections of three patients with SLE but not in six control kidneys. The immunofluorescence reaction was mediated by three hyperimmune antisera to IFN-alpha raised in three different species, but not by any preimmune serum. The reaction was specifically blocked by absorption of the anti-IFN-alpha sera with purified IFN-alpha made by recombinant DNA techniques or with IFN-alpha isolated from the serum of an SLE patient, but not by bovine serum albumin or human immunoglobulin G. In contrast, antisera to IFN-beta or IFN-gamma did not mediate immunofluorescence. The pattern of IFN-alpha deposition resembled that seen with anti-human immunoglobulin G, suggesting association with immune complexes. Immune complexes were then preparatively eluted from the homogenate of an SLE kidney by treatment with buffer at pH 2.8. Biologically active IFN was found in this eluate and was demonstrated to be IFN-alpha by specific neutralization with IFN antisera. These results extend the specific association of IFN-alpha with SLE.