Microassay for colorimetric estimation of complement activity in guinea pig, human and mouse serum

A sensitive colorimetric microassay for determining haemolytic complement activity was devised. It is carried out in U-welled microtitre dishes covered with plastic tape, which are incubated in a waterbath and subsequently centrifuged. The supernatant is transferred to flat-bottomed microtitre dishes and haemolysis is estimated by automatic measuring of the absorption using an interference filter of 405 nm in a Titertek Multiskan. Advantages of the method described are saving time and materials, and avoiding the use of radioactive nuclides. This microassay may therefore be a useful substitute for macro and semi-micro tests for colorimetric determination of serum complement activity and for microassays based on the release of a radio-isotope.