The parent-into-immunocompetent-F1 model of graft-vs-host disease (GVHD) induces immune dysregulation, resulting in acute or chronic GVHD. The disease outcome is thought to be determined by the number of parental anti-F1 CTL precursor cells present in the inoculum. Injection of C57BL/6 (B6) splenocytes into (B6 × DBA/2)F1 (B6D2F1) mice (acute model) leads to extensive parental cell engraftment and early death, whereas injection of DBA/2 cells (chronic model) results in little parental cell engraftment and a lupus-like disease. This study demonstrated that injection of BALB/c splenocytes into (BALB/c × B6)F1 (CB6F1) mice resulted in little engraftment of parental lymphocytes and the development of lupus as expected. Injection of B6 splenocytes into CB6F1 initiated an initial burst of parental cell engraftment similar to that of B6 into B6D2F1. However, the acute disease resolved, and the CB6F1 mice went on to develop chronic GVHD with detectable Abs to ssDNA, dsDNA, and extractable nuclear Ags. Limiting dilution CTL assays determined that B6 splenocytes have CTL precursor frequencies of 1/1000 against both CB6F1 and B6D2F1, whereas DBA/2 and BALB/c splenocytes have a CTL precursor frequency of 1/20,000 for their respective F1s. The Th cell precursor frequency for B6 anti-DBA/2 was 3-fold higher than that for B6 anti-BALB/c determined by limiting dilution proliferation assays. These results indicate the importance of adequate allospecific helper as well as effector T cells for the induction and maintenance of acute GVHD in this model, and presents an unexpected model in which initial acute GVHD is replaced by the chronic form of disease.
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