Inhibition of polymorphonuclear leukocyte chemiluminescence for detection of immune complexes in human sera.

An assay for the detection and quantitation of immune complexes is described. Experimental immune complexes or aggregated human gamma globulin (AHG) were incubated with polymorphonuclear leukocytes (PMN). After challenge of the PMN with opsonized zymosan, chemiluminescence was recorded in a scintillation spectrometer. A quantitative inhibition of chemiluminescence could be demonstrated by the interaction of PMN with immune complexes or AHG. Experimental immune complexes of bovine serum albumin-anti-bovine serum albumin were formed and tested by this assay, and immune complexes formed near antigen excess were best described by this technique. The technique was used to demonstrate immune complexes in the sera from patients with systemic lupus erythematosus, rheumatoid arthritis, and vasculitis. Immune complexes were quantitated by reference to a standard curve using AHG. By this technique, normal human sera had < 10 micrograms of AHG per milliliter of serum. Immune complexes at levels above this were detected in 9/15 patients with systemic lupus erythematosus, 18/30 patients with rheumatoid arthritis, and 2/5 patients with vasculitis. Therefore, this assay is a sensitive, simple method for measurement of circulating immune complexes in the sera of patients with certain connective tissue diseases.