The expression of alternative pathway-mediated haemolysis by sera from selected animals.

The kinetics of aIternative-pathway mediated haemolysis were studied in sera from a number of vertebrate species. Rabbit erythrocytes in a veranol buffer supplemented with magnesium chloride and ethylene glycol bis tetraacetic acid (EGTA) were used as a target for these assays. Human sera showed significant variations in the kinetics of the lytic reaction at dilutions above 1:2. A number of factors appeared to contribute to these variations and no single determinant of reaction kinetics could be identified. Sera from domesticated and feral animals showed little variation within any species, but marked differences were seen between the species studied. Badger, ferret and hedgehog exhibited potent alternative pathway activity while mouse serum showed very little. The results of kinetic assays of alternative pathway haemolytic activity and total haemolytic complement activty were compared with those of conventional, endpoint, assays. No classical pathway activity could be elicited from mouse serum. Inbred strains of mice showed significant differences in the kinetics of alternative pathway mediated haemolysis between the males and females of each strain examined, and between some of the strains examined. These differences did not affect the spread of mycobacteria after subcutaneous and intravenous injection. Human sera with a defective ability to opsonise yeasts showed normal lytic activity in the kinetic assay. In contrast, sera from children and adults with obsructive jaundice which exhibit enhanced opsonic activity also showed accelerated reaction kinetics in the lytic assay