Alternate complement pathway in porcine sera: Lysis of guinea pig erythrocytes

The hemolysis by porcine sera of unsensitized erythrocytes (EU) from nine different species was investigated. Optimal lysis occurred when porcine sera were reacted with unsensitized guinea pig erythrocytes suspended in a pH 6.5, barbital-buffered saline solution, made 0.1% in gelatin, and containing 10 mm ethyleneglycol-bis (β-amino-ethyl ether) N, N¹-tetraacetic acid and 4 mm MgCl₂ (BSG-EGTA-Mg). Results of studies with several different treatments that inhibit complement (C) induced hemolysis indicated that the alternate C pathway was involved in the lysis of EU in the BSG-EGTA-Mg buffer. The extent of lysis was decreased when porcine sera were adsorbed with zymosan, mixed with 20 mm salicylaldoxime, or heated at 50%C. However, carrangeenan treatment caused only a slight decrease in the extent of hemolysis induced. Cobra venom factor activated the alternate C pathway in porcine sera. The pattern of C component utilization resulting from lysis of EU by porcine sera indicated activation of the alternate and not the classical C pathway. Extensive adsorption of porcine sera with packed guinea pig erthrocytes at 0°C only slightly reduced its capacity to lyse guinea pig erythrocytes. Collectively, these results provided evidence that the membrane of the guinea pig erythrocyte is able to active the alternate C pathway of porcine sera without the direct involvement of specific antibody.