Altered T‐cell entry and egress in the absence of Coronin 1A attenuates murine acute graft versus host disease

Acute graft‐versus‐host disease (aGvHD) is a major limitation to the use of allogeneic stem cell transplantation for the treatment of patients with relapsed malignant disease. Previous work using animals lacking secondary lymphoid tissue (SLT) suggested that activation of donor T cells in SLT is critically important for the pathogenesis of aGvHD. However, these studies did not determine if impaired migration into, and more importantly, out of SLT, would ameliorate aGvHD. Here, we show that T cells from mice lacking Coronin 1A (Coro 1A^?/?), an actin‐associated protein shown to be important for thymocyte egress, do not mediate acute GvHD. The attenuation of aGvHD was associated with decreased expression of the critical trafficking proteins C‐C chemokines receptor type 7 (CCR7) and sphingosine 1 phosphate receptor on donor T cells. This was mediated in part by impaired activation of the canonical NF‐κB pathway in the absence of Coro 1A. As a result of these alterations, donor T cells from Coro 1A^?/? mice were not able to initially traffic to SLT or exit SLT after BM transplantation. However, this alteration did not abrogate the graft‐versus‐leukemia response. Our data suggest that blocking T‐cell migration into and out of SLT is a valid approach to prevent aGvHD.