Anticomplementarity in complement-fixation test with soluble antigens of the spotted fever group rickettsiae.

Anticomplementarity occurring in the complement-fixation (CF) test with soluble antigens of rickettsiae of the spotted fever (SF) group is caused by interaction of soluble antigens with guinea pig sera serving as the source of complement. The serum factor responsible for anticomplementarity is thermostable and cannot be removed by treatment of guinea pig serum with CO2 or nitrogen. An adverse effect of such serum was also observed upon its mixing with other guinea pig sera lacking anticomplementarity properties. An anticomplementarity factor present in the soluble rickettsial antigens was sensitive to treatment with potassium periodate.