The cohort has been dichotomized according to the recipient's CMV reactivation status (■ n=152, having at least one incident of CMV reactivation; and n=59, having no CMV reactivation). The KIR gene frequency is separately portrayed for donors (Panel A) and recipients (Panel B). aKIR2DS4d represents the deletion variant of aKIR2DS4. iKIR2DL4, iKIR3DL2 and iKIR3DL3 were detected in all members of this cohort, and thus omitted from this figure. AA indicates individuals homozygous for KIR haplotype A, and BX indicates individuals either heterozygous (BA) or homozygous (BB) for KIR haplotype B. * p= 0.06, ** p≤ 0.05 using the Chi-square test.