Quantitative studies of the interaction of 3H-dsDNA/anti-DNA immune complexes with complement: comparison and evaluation of the Raji cell, the solution phase C1Q, and the red blood cell linked complement fixation radioimmunoassays.

We have prepared antibody/3H-dsDNA immune complexes and have used three independent radioimmunoassays to quantitate their interaction with complement; the solution phase C1q assay, the Raji cell assay, and a complement-based red blood cell adherence assay (RBC-CF). Our results indicate that although there is reasonable qualitative agreement between the Raji cell assay and the RBC-CF assay, there are some differences in the quantitative range of sensitivities of the two assays. On the other hand, we find that most of the complement-fixing antibody/3H-dsDNA complexes are not detected in the solution phase C1q assay. The results suggest this is because the absolute concentrations of the immune complexes were too low to achieve significant precipitation under the standard conditions used in the C1q assay. The implication of these findings with respect to the potential detection and analysis of antibody/dsDNA immune complexes is discussed.