Antibody complement-mediated hemolytic studies with kodecytes reveal that human complement utilized in the classical...

Complement has significant status in the field of transfusion medicine. The accepted stability profile of complement is based on historical studies of diluted human serum hemolyzing rabbit heterophile antibody-sensitized sheep red blood cells (RBCs). Contemporary tools are available to reevaluate these historical observations using human heterophile antibodies, undiluted serum, and antigen-modified human RBCs.

Human RBCs were made into "animal-like" kodecytes with heterophile Galα3Galβ4GlcNAcβ function-spacer-lipid constructs. These α-Gal-kodecytes were prepared with an antigen dilution capable of consistently producing 50% antibody-mediated hemolysis against human α1-3galactose heterophile antibodies and undiluted standardized serum. Standardized human serum aliquots from a two-donor pool stored at -85, -20, 4, 22, and 37°C for durations of up to 150 days were evaluated for loss of hemolytic activity. Where practical methodologic procedures were aligned with historical studies.

Comparison of the historical assay with the α-Gal-kodecyte assay against complement activity standards showed concordance. However, in most scenarios complement was found to be more than twice as stable as generally accepted. At least 60% of complement hemolytic activity was observed in serum stored at 22°C for 1 week or 2 months at 4°C. No loss of hemolytic activity was observed after 5 months' storage at temperatures below -20°C.

An alternative method using undiluted serum and modified human RBCs observed that classical-pathway complement hemolytic activity in stored human serum is at least twice as stable as previously accepted.