The presence of the fifth component of complement (C5) in rabbit uterine flushings in relation to reproductive state.

The fifth component of complement (C5) has been detected in rabbit uterine flushings. The C5 activity was evaluated using a hemolytic assay which requires the use of a C5-depleted reagent (C5D) prepared by affinity chromatography of normal human serum. In the absence of C5D, there was no hemolysis of antibody-sensitized erythrocytes by rabbit uterine flushings, whereas the presence of the C5D reagent resulted in substantial hemolysis. The amount of hemolysis was correlated with the reproductive state of the rabbits, with higher amounts of hemolysis (expressed per mg uterine flushing protein) evident in estrous rabbits. In addition, the amounts of immunoglobulin G (IgG), albumin, and total protein were also determined in the uterine flushings. The amounts of total protein and IgG were increased in day-6 pregnant animals compared to estrus while the amount of albumin per ml uterine flushing was not significantly changed.