Mobilized Mouse and Human Peripheral Blood Containing Elevated Numbers of Donor Treg Cells Ameliorates Pre-Clinical GvHD and GVL Is Maintained in an MHC-Matched Allogeneic Murine Model

Mobilized hematopoietic stem / progenitor cells have become the primary option used for adult allogeneic hematopoietic stem cell transplants (aHSCTs) although GVHD remains a major immunologic complication (CIBMTR, 2017). The present studies are directed to developing a translational model for the application of donor regulatory T cells (Tregs) together with the use of mobilized peripheral blood (mPB) for more widespread application of these aHSCTs. We have previously reported that two-pathway Treg expansion strategy markedly elevates Treg numbers and function (Wolf, 2017; Copsel 2018). Additionally, this approach could be effectively applied in a concomitant strategy to amplify Treg suppressor activity in mPB to diminish pre-clinical GVHD (Barreras H, ASTCT Meeting S292 ,2019). Here, we present new findings using mPB transplants examining GVL reactivity in an MHC-matched minor antigen mismatched pre-clinical model and test the notion that human donor Tregs can be employed with mobilized healthy donor PB to effectively regulate xenogeneic GVHD.