CD45.1/CD45.2 congenic markers have been used to track hematopoietic lineage differentiation following hematopoietic stem and progenitor cell (HSPC) transplantation. However, several studies suggest that a bias exists in CD45.1 versus CD45.2 hematopoietic cell reconstitution from HSPCs. Meanwhile, no definitive comparison has been reported for mature immune cells as to whether the CD45.1/CD45.2 disparity can skew the immune cell response. In this study, using lymphocytopenia Rag1-/- CD45.2 mice as hosts, we assessed the reconstitution potential of CD45.1 versus CD45.2 lymphocytes following adoptive transfer of mature T and B cells. We have found a selective bias for CD8+ T cells in that CD45.1 cells showed significantly higher reconstitution compared with CD45.2 cells, whereas CD4+ T cells and CD19+ B cells showed equivalent reconstitution. These results suggest that CD45.1/CD45.2 markers may induce an alloreactive response or a survival bias specific to CD8+ T cells, and they therefore call for caution for using them as congenic markers in immunologic models.
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