PDCD1 and graft versus host disease: ICIs are utilized to enhance anti-tumor immune responses by targeting inhibitory receptors found on immune cells, including cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1).39 The utilization of animal models has played a crucial role in comprehending the mechanisms that underlie the anti-tumor impacts of ICIs and predicting their clinical efficacy.10 The emergence of GVHD in these models may interfere with the comprehension of ICI efficiency and adverse effects.34