L-selectin is dispensable for T regulatory cell function postallogeneic bone marrow transplantation

In murine models, the adoptive transfer of CD4⁺/CD25⁺ regulatory T cells (T_regs) inhibited graft-versus-host disease (GvHD). Previous work has indicated a critical role for the adhesion molecule L-selectin (CD62L) in the function of T_regs in preventing GvHD. Here we examined the capacity of naive wild-type (WT), CD62L^-/- and ex vivo expanded CD62L^Lo T_regs to inhibit acute GvHD. Surprisingly, we found that CD62L^-/- T_regs were potent suppressors of GvHD, whereas CD62L^Lo T_regs were unable to inhibit disease despite being functionally competent to suppress allo T cell responses in vitro. Concomitant with improved outcomes, WT and CD62L ^-/- T_regs significantly reduced liver pathology and systemic pro-inflammatory cytokine production, although CD62L^-/- T_regs were less effective in reducing lung pathology. While accumulation of CD62L^-/- T_regs in GvHD target organs was equivalent to WT T_regs, CD62L^-/- T_regs did not migrate as well as WT T_regs to peripheral lymph nodes (PLNs) over the first 2 weeks posttransplantation. This work demonstrated that CD62L was dispensable for T_reg-mediated protection from GvHD.