Antibody to DNA in human serums can be detected by the ammonium sulfate method. This sensitive and specific technique, which measures the primary interaction between DNA and antibody to DNA, is based on the observation that free DNA is soluble in 50-percent saturated ammonium sulfate whereas antibody-bound DNA is insoluble.

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Summary The effect of ε-aminocaproic acid (EACA) treatment of rabbit anti-bovine serum albumin (BSA) was studied in vitro. Primary binding and spontaneous precipitation of I131 BSA by rabbit anti-BSA were not affected by EACA concentrations as high as 7 × 10-3M, but were partially inhibited by 3 × 10-2M and higher. The inhibitory effect of the higher concentrations of EACA was completely reversible by dialysis of the treated antisera, indicating no permanent alteration of the BSA binding or precipitating capacity. Anti-BSA hemagglutination titers were not altered by EACA concentrations as high as 7 × 10-2M and we were unable to confirm the reported inhibitory effect of EACA upon human isoagglutinins. Thus, if EACA in a concentration comparable to current human therapeutic plasma levels of 10-3M has any effect on immune mechanisms, it does not affect the primary binding or secondary manifestations of the antigen-antibody reaction as measured by the in vitro techniques employed.