Role of self carriers in the immune response and tolerance. X. A lymphoid dendritic-like tumor, P388AD.2, acts as a novel immunogenic carrier for hapten

Hapten-modified spleen cells, peritoneal exudate cells, and certain lymphoid tumors preferentially induce specific tolerance after i.v. administration. In contrast to these tolerogenic carrier cells, we found that a haptenated lymphoid dendritic-like tumor, P388AD.2, acts as a potent immunogen after i.v. injection. The immunogenicity of P388kAD.2 was analyzed by measuring the specific augmentation of plaque-forming cell (PFC) responses when spleen cells from mice previously injected with haptenated tumor cells were challenged in vitro with thymus-independent antigens. Optimal immunization was found to be dependent on cell dose and hapten concentrations. Further studies indicated that P388AD.2 elicited a response which was T cell-dependent and which involved both the so-called Lyb-3,5,7^- and Lyb-3,5,7⁺ B cell populations. Injection of haptenated tumor into different mouse strains suggested that H-2 compatibility was required to prime B cells in vivo, although significant augmentation could also be achieved in allogeneic C57Bl/6J mice. The enhanced PFC responses elicited in H-2^b mice could not explained by allo-recognition of class I or II MHC determinants. In toto, these results suggest that P388AD.2 acts as a unique accessory cell for the presentation of hapten-modified self.