A novel alloantigen on rat macrophages and granulocytes.

Previous studies have shown that immunization of MAXX rats with spleen and lymph node cells from the MHC-identical BN strain results in the formation of antibodies that react with the renal endothelial alloantigen Eag-1. In the present study, the reactivity of MAXX anti-BN sera was further characterized. No reactivity of the antisera was detected with unseparated spleen, lymph node, thymus and bone marrow cell suspensions, peripheral blood, or cells obtained from lung lavages. The antisera did, however, react with splenic macrophages, as well as with peritoneal granulocytes and macrophages from BN, BN.1A, BN.1L, and PVG rats. Genetic studies revealed that the antigen, provisionally designated Pag-1, segregates independently of Eag-1, the RT1 complex, sex, and the hooded and albino traits. Pag-1 appears to be absent in the kidney, since absorption of MAXX anti-BN sera with BN kidney homogenates did not remove the reactivity against Pag-1, and antisera raised against BN peritoneal cells did not bind with the renal endothelium. Pag-1 is expressed on bone marrow-derived cells, since peritoneal cells from lethally irradiated MAXX rats that were reconstituted with bone marrow cells from BN donors reacted with MAXX anti-BN sera, whereas peritoneal cells from BN rats reconstituted with MAXX bone marrow did not.