An improved quantitative micro-complement fixation test.

The technical procedures for a simple quantitative micro-complement (C) fixation test are described. Major advantages of the present technique compared with the previously described method are: a) a simple measurement of the residual hemolytic activity of C by counting the radioactivity released from 51Cr-labeled sensitized sheep erythrocytes (51Cr-EA); b) an increased sensitivity of the test, brought about by the use of a relatively small number of 51CR-EA per reaction volume; and c) an increased specificity of the test, achieved by maintaining a constant amount of C available for the specific antigen--antibody reaction.