Estimation of classical pathway of mouse complement activity by use of sensitized rabbit erythrocytes

A simple photometric assay was devised for determining classical complement pathway activity in mouse serum using sensitized rabbit erythrocytes as target cells. These cells appeared more sensitive to lysis by mouse complement than sensitized mouse and sheep erythrocytes, most probably by their ability to escape the C3b inactivator system. Advantages of the assay over other techniques are the high sensitivity and the avoidance of the use of radioisotopes. With this test it is possible to get more insight in the complement system of an animal species that has been most widely in use in immunological research.