Complement Fixation Sheep RBC Sheep RBC Y Y Antibody to Antibody to sheep RBC sheep RBC a661s ojeolpul No hemolysis Hemolysis (complement tied up in antigen-antibody reaction) (uncombined complement available) (a)Positive test.All available complement is fixed by (b)Negative test.No antigen-antibody reaction occurs. the antigen-antibody reaction:no hemolysis occurs, The complement remains,and the red blood cells are so the test is positive for the presence of antibodies. lysed in the indicator stage,so the test is negative. Figure 18.9.2 Complement Fixation Figure 18.9.2