Hemolysis by the complement of tanned erythrocytes coated with cobra venom factor: a sensitive method to detect the alternative complement pathway activity of serum.

Sheep (Esh), human (Ehu), rabbit (Erab) or guinea pig (Egp) erythrocytes were treated with tannic acid and coated with cobra venom factor (CoVF), which activates the alternative complement pathway (ACP). Tanned erythrocytes (TE) coated with CoVF (TECoVF) were efficiently hemolyzed by guinea pig serum l(GPS) and/or rabbit serum (RabS) in Mg2+-EGTA-GVB (gelatin veronal-buffered saline containing 2 mM MgCl2 and 10 mM ethyleneglycol-bis(beta-aminoethyl ether)N,N'-tetraacetate). The reactivity of TEsh-CoVF, TEhu-CoVF and TErab-CoVF to the ACP of guinea pig and/or rabbit increased with the increased amount of CoVF fixed on TE until it was sensitive enough to be hemolyzed by serum diluted over 80 times in Mg2+-EGTA-GVB. The hemolysis of TECoVF by GPS was confirmed to be the result of ACP activation by the findings that the reaction was inhibited in EDTA-GVB, heating of GPS at 50 degrees C diminished its hemolytic potency, and fractions of factor B and factor D were essential to the sensitization of TECoVF for hemolysis by GPS in EDTA-GVB. On the other hand, none of the TE coated with CoVF were hemolyzed by human serum (HuS) diluted over 1 : 40. Although the low efficiency of HuS in TE-CoVF hemolysis remains to be explained, TE-CoVF will be useful for the detection of ACP activity of guinea pig and rabbit sera.