A C1q Immunosorbent Assay Compared with Thin-Layer Gel Filtration for Measuring IgG Aggregates

A new sensitive technique measures C1q-binding of human IgG aggregates. The method is based on the principle of the enzyme-linked immunosorbent assay with C1q-coated tubes. The IgG aggregates attaching to this C1q are shown by enzyme-linked anti-human IgG. Less than 0.01 mug of aggregates per milliliter of sample can be detected. The results with this new method showed significant correlation (P less than 0.01; Spearman rank correlation test) with the estimates of IgG aggregates of 13S or more and 10S in size obtained by thin-layer gel filtration. Both of these methods showed significant correlation with the classic hemolysis inhibition method for measuring complement fixation.