An experimental model for preventing alloimmunization against platelet transfusions by pretreatment with antibody-coated cells.

The pretreatment of LEW (RT-1l) rat recipients with antibody-coated BN (RT-1n) blood cells resulted in the suppression of the LEW antibody response against subsequent BN platelet and leukocyte transfusions. Both coating with homologous LEW-anti-BN serum or heterologous rabbit-anti-rat lymphocyte serum was effective. Repeated boosting with uncoated platelets or leukocytes did not abrogate the suppression. The degree of suppression was dependent on the amount of antibody used for cell coating. The induced suppression was also extended to uncoated antigens and unrelated third-party cells. The serum-IgG fraction of pretreated rats was strongly immunosuppressive, suggesting that the mechanism of suppression was related to the induction of a broadly reactive regulatory IgG.