Immunologic cross-reactions between the specifically localizing cells (SLC) generated in response to sheep RBC and the red cells of other species.

Some of the lymphoid cells selectively incorporating radioactive thymidine 3 days after primary immunization with SRBC which are capable of specifically localizing in the lymph nodes of adoptively immunized syngeneic recipients challenged with SRBC (SLC-SRBC)2 are also capable of specifically localizing in lymph nodes challenged with the red blood cells of a varieth of other mammalian species. The one nonmammalian RBC tested, CRBC, failed to cross-react with SRBC by this parameter even qualitatively, although it remains possible that a feeble cross-reaction might be demonstrated with large enough experimental groups. As expected, the magnitude of the observed cross-reactions seems to vary inversely with the phylogenetic distance between the species, with ORBC showing the strongest cross-reaction (41 to 49%), ARBC showing the weakest (8 to 13%), and BRBC and HRBC occupying intermediate positions (13 to 20%). Cross-reaction between secondary anti-SRBC antibodies and the red cells of the other species were weak and inconstant, suggesting that the observed cross-reactions of specific localization may involve T cells more than B cells. During the course of these studies, it was also possible to verify experimentally our impression that with existing methods of selectively labeling SLC it is possible to study the phenomenon of specific localization using only one population of labeled cells, providing certain essential controls are employed.