The humoral immune response during adult graft-versus-host reaction (GVHR) was assessed by the recovery of antibody-forming host spleen cells using cell fusion techniques. Two parent → F1 strain combinations were studied, (B6 × D2)F1 and (NFS × AKR)F1 injected with the respective parental spleen cells. Hybridomas derived from recipient spleens were found to produce antibody with predominant specificity for murine leukemia virus (MuLV) envelope (env) polypeptides. The recovery of anti-MuLV monoclonal antibodies was dependent on the donor strain. Thus, D2 → (B6 × D2)F1 and AKR → (NFS × AKR) resulted in a high incidence of anti-MuLV antibody production among the primary fusion products whereas no anti-MuLV hybridomas were recovered when B6 or NFS, respectively, were used as donors. Hybridomas derived from D2 → (B6 × D2)F1 produced anti-MuLV antibodies of two general specificities: (1) broadly reactive, detecting determinants expressed by ecotropic and xenotropic MuLV, and (2) xenotropic MuLV specific. The latter group included antibodies reacting with all xenotropic MuLV and antibodies with xenotropic MuLV strain specificity. Xenotropic MuLV-specific determinants tere expressed by gp70, p15(E), and the gp70-p15(E) complex (gp90). This is to our knowledge, the first report of monoclonal antibodies specific for xenotropic MuLV. In contrast, hybridomas derived from AKR → (NFS × AKR) produced antibodies which reacted predominantly with unique determinants of a subgroup of MCF viruses. These results suggested that the anti-MuLV antibody repertoire expressed during GVHR is influenced by the endogenous MuLV of the respective mouse strain combination.
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