Experiments with immunization of mice with blastocysts by an intrasplenic route

A few attaching blastocysts from CBA/H mice were irradiated from a Cesium source and transferred into the spleen of male DBA2 mice. A booster immunization was performed after four weeks. Blood samples for preparation of antiserum to test for the presence of immunoglobulins directed against blastocyst surface determinants were obtained by a retro-orbital puncture. Specific antibodies were detected with a protein A-gold method, modified for transmission electron microscopy of air-dried blastocysts. The results showed that CBA/H blastocyst incubated in DBA2 immune serum were positive for protein A-gold labelling, while control blastocysts only possessed a few irregularly scattered gold particles. Thus, it seems as a deposition of antigens in the spleen tissue with persistence of the antigens at this site will result in detectable antibodies in the peripheral blood.