Effective induction of anti-phospholipid and anticoagulant antibodies in normal mouse.

Anti-phosphatidylserine (anti-PS) antibodies of the IgG isotype in the serum of BALB/c mouse were effectively induced by the intrasplenic immunization of phosphatidylserine (PS), while only a slight increase of the titer was observed when the antigen was injected intravenously. The serum antibodies cross-reacted extensively with other acidic phospholipids, but not with phosphatidylcholine (PC). A remarkable frequency of anti-PS mAbs of the IgG isotype was also observed even when mAbs were produced 10 days after the intrasplenic injection of the antigen. Reactivities of the fifteen mAbs, which had been established from BALB/c mice by the intrasplenic immunization with PS, were further analyzed. Among the fifteen mAbs examined, thirteen cross-reacted with ssDNA and two bound to dsDNA. Seven mAbs had lupus anticoagulant activity and four bound to cultured human umbilical vein endothelial cells (HUVECs). No significant correlation was found among phospholipid specificities, anti-DNA, anticoagulant, and HUVEC binding activities. One mAb of the IgG2b subclass, named PSG3, which had been produced 10 days after the immunization, was shown to have a strong lupus anticoagulant, dsDNA binding, and HUVEC binding activities.