Rat-mouse radiation chimeras: characterization of an antibody-mediated graft-vs-host reaction.

A modification of the Jerne hemolysis-in-agar technique was used to demonstrate antibody-mediated graft-vs-host (GvH) hemolytic activity in lymphoid tissues of rat-mouse radiation chimeras. Initial foci of hemolytic activity were detected on the 3rd day in spleens of lethally x-irradiated mice infused with rat spleen cells (950 R-RSp chimeras). The peak of GvH foci response occurred near the end of the 1st week when 70% of 950 R-RSp chimera spleens examined contained an average of 18 to 21 foci per spleen. GvH hemolytic activity was also detected in mice reconstituted with rat bone marrow (950 R-RBM chimeras); however, only 40% of these chimeras contained splenic foci (nine foci per spleen) on day 8, the peak day of response. Mesenteric lymph nodes from 950 R-RSp chimeras, but not 950 R-RBM chimeras, also contained GvH hemolytic foci. Specificity experiments demonstrated that the GvH hemolytic reaction could be inhibited with rabbit anti-rat IgM serum and host (C3BF) antigenic cell fragments. Indirect (IgG) hemolytic activity was also observed in spleens of 950 R-RSp chimeras 6 to 10 days after treatment. At least 90% of indirect foci appeared coincident with direct foci. Rat IgM and IgG containing cells beneath hemolytic foci were observed by combining the fluorescent antibody and foci techniques. To determine whether the foci response reflects and in vivo sensitization of donor cells, spleen cell transfer experiments were done. The results indicate that spleen cells from 950 R-RSp chimeras were more effective in acelerating mortality and anemia and induced a higher incidence of Coomb's positive red cells in lethally irradiated isogeneic recipients than spleen cells from 950 R-RBM chimeras; spleen cells from either chimera were more effective in accelerating GvH indices than spleen and marrow cells from normal rats.