Antibodies to liposomal phosphatidylcholine and phosphatidylsulfocholine

Antibodies against dimyristoyl phosphatidylsulfocholine or dimyristoyl phosphatidylcholine were raised in rabbits after injection of liposomes containing phosphatidylsulfocholine or phosphatidylcholine, cholesterol, and lipid A. The antibody activities were assayed by complement-dependent immune damage to liposomes and by a solid-phase, enzyme-linked immunosorbent assay using purified dimyristoyl phosphatidylcholine or dimyristoyl phosphatidylsulfocholine as antigen. Each antiserum raised against phosphatidylsulfocholine reacted with liposomes containing phosphatidylcholine, and each antiserum raised against phosphatidylcholine reacted with liposomes containing phosphatidylsulfocholine. However, adsorption of dimyristoyl phosphatidylsulfocholine antiserum with liposomes containing dimyristoyl phosphatidylcholine removed all activity against dimyristoyl phosphatidylcholine, but did not eliminate antibody activity against dimyristoyl phosphatidylsulfocholine. These results indicate that the antiserum against phosphatidylsulfocholine contained mixed populations of antibodies. Polyclonal antisera that have been appropriately adsorbed can therefore be obtained with a high degree of specificity for phosphatidylsulfocholine and such antisera can distinguish between phosphatidylsulfocholine and phosphatidylcholine.