Differential extraction of antigens of Anaplasma marginale

Strain-, group-, and genus-specific antigens of the Florida isolate of Anaplasma marginale had different solubilities in zwitterionic, nonionic, and anionic detergents. On the basis of their solubility in nonionic detergent, antigens were grouped into 3 classes: (i) a 108-kilodalton (kD) group-specific antigen and a series of poorly defined antigens (70 to 100 kD) were completely soluble in nonionic detergent; (ii) 96 kD and 75 kD group-specific antigens, and a 91-kD strain-specific antigen were completely insoluble in nonionic detergent; and (iii) a 47-kD group-specific antigen and a 41-kD genus-specific antigen were partially soluble in nonionic detergent. A mercaptoethanol-sensitive antigen of 200 kD also was present in the insoluble fraction. Differences in solubility of taxonomic antigens of Anaplasma may reflect differences in function. Antigens totally insoluble in nonionic detergent were possibly integral membrane proteins, and those completely soluble in nonionic detergent were more likely peripheral membrane proteins that were less tightly bound to hydrophobic components of the membrane. Seemingly, all antigens were associated with membranes. Bovine preimmune and immune sera used did not react with any proteins of noninfected RBC.