OBSERVATIONS ON PH + HAEMOLYTIC COMPLEMENT

Abstract

The effect of pH on the haemolytic activity of guinea-pig complement was studied over the range 6.0-8.3 using veronal-acetate and bicarbonate buffers of essentially constant ionic strength and osmolality. Complement in both buffer systems showed maximum haemolytic activity at a pH value close to 6.8. The reaction EA [forward arrow] EAC[image]142 took place optimally at pH 6.8 at 1[degree] but the reaction in which EAC[image]142 was lysed by C[image]3 at 37[degree] was scarcely affected by pH over the range 6.0-8.2. Fixation of complement by heat-aggregated [gamma]-globulin, by a globulin-anti-globulin precipitate and by polio vaccine plus antibody increased steadily as the pH was raised from 6.15 to 8.5. Beyond pH 8.5 complement itself was unstable. A four-fold increase in the sensitivity of the complement-fixation test was obtained by raising the pH from 7.0 to 8.3.