TIGIT Blockade Potentiates the Anti-Leukemic Activity of Exercise-Mobilized Donor Lymphocytes and Expanded γδ T-Cells.

Donor lymphocyte infusion (DLI) is commonly used to prevent or treat leukemic relapse following allogeneic hematopoietic cell transplantation; however, efficacy is limited by immune exhaustion, checkpoint-mediated inhibition, and the risk of graft-versus-host disease (GvHD). Gamma delta (γδ) T-cells represent a promising "off-the-shelf" adoptive cell therapy (ACT) with favorable safety and MHC-independent cytotoxicity, yet their function is similarly constrained by the leukemic tumor microenvironment (TME). Acute exercise mobilizes cytotoxic lymphocyte subsets, and is an emerging strategy to enhance cellular immunotherapies, including DLI and expanded γδ T-cells. This study examined how exercise-mobilized lymphocytes and exercise-expanded γδ T-cells interact with TIGIT blockade to improve anti-leukemic activity. Healthy participants completed an acute cycling bout, after which peripheral blood mononuclear cells (PBMCs) and ex vivo expanded γδ T-cells were phenotyped and cytotoxicity was determined against leukemia cells with TIGIT checkpoint inhibition. The therapeutic relevance of combining TIGIT blockade with rest- or exercise-expanded γδ T-cells was further evaluated in NSG-IL15 mice challenged with K562-luc leukemia. Acute exercise increased circulating CD8 and γδ T-cells with higher TIGIT and PD-1 expression. Exercise-expanded γδ T-cells maintained increased PD-1 and TIGIT expression and exhibited increased co-expression of DNAM-1 and TIGIT. Exercise mobilized PBMCs and exercise-expanded γδ T-cells demonstrated enhanced cytotoxicity, further amplified by TIGIT blockade. In vivo, TIGIT-treated exercise-expanded γδ T-cells modestly improved tumor suppression and prolonged tumor-free survival compared to untreated controls. Exercise primes DLI and γδ T-cell products for enhanced responsiveness to TIGIT checkpoint inhibition. Targeting TIGIT likely augments DNAM-1 dependent cytotoxicity and improves anti-leukemic activity, supporting the integration of exercise-enhanced DLI and γδ T-cell therapies with immune checkpoint blockade as a safe strategy to improve relapse control in leukemia.