CTLA4 and graft versus host disease: The A allele of rs231775 on exon 1 of CTLA4 (allele model: p = 0.0343 for A vs. G, OR = 2.28, and 95% CI = 1.07–4.89), the A allele of rs41386349 (allele model: p = 0.0436 for A vs. G, OR = 2.71, and 95% CI = 1.03–7.1), the T allele of rs6705653 (Trend test: p = 0.0086; allele model: p = 0.0039 for T vs. C, OR = 3.53, and 95% CI = 1.51–8.28) in the intron 4 of PDCD1, and the G allele of rs2227982 (Trend test: p = 0.0194; allele model: p = 0.0055 for G vs. A, OR = 3.4, and 95% CI = 1.44–8.03) in the exon 5 of PDCD1 gene contributed to a higher risk for mild GVHD.