Although there is not extensive literature regarding the consequences in pathological conditions of γδ T-cell exhaustion, PD-1 upregulation in activated γδ T cells has been associated with reduced IFNγ secretion in leukemia patients59, reduced cytotoxicity against several PD-L1-expressing tumor cell lines61, and impaired αβ T-cell function30. This evidence concerns the gene PDCD1 and leukemia.