Immunological comparison of phospholipases A2 present in rattlesnake (genus Crotalus) venoms

The immunological properties of phospholipase A₂ present in venoms from seven species of rattlesnakes (genus Crotalus) from different geographical distributions have been compared. Rabbit antiserum to purified PLA₂ of Crotalus scutulatus salvini venom was used, employing inhibition of enzymic activity and immunodiffusion techniques. The amount of antiserum required for 50% inhibition of the PLA₂ activity in the venoms varied from slightly more than that required for inhibition of the activity in the homologous venom to a large amount (effectively zero inhibition). A particularly close relationship in the antigenic makeup was observed between the phospholipases of C. s. salvini and C. atrox venoms as evidenced by inhibition of enzymic activity and immunodiffusion studies. No immunological cross reactivity was observed between the enzymes of the subspecies C. s. salvini and C. s. scutulatus. The results suggest extensive variations in the antigenic structure of the phospholipase molecules. The findings may also have some taxonomic significance.