In this article we examined the role of HLA incompatibility, of KIR C1 and C2 ligands and of other clinical factors on 99 cord blood transplants performed using single units from Milano Cord Blood Bank (MICB). We analyzed the occurrence of rejection, overall patient survival (OS) and occurrence of acute GvHD ≥2 grade (severe aGvHD). No correlation was found between the end points and the number of HLA-A,-B, -DRB1 and -DQB1 mismatches. Only HLA-C disparities are associated with the occurrence of rejection (P = 0.03). Our results showed that the presence of the C1 ligand in the donor decreased the occurrence of aGvHD (grade ≥2) in the recipient while recipients of donors expressing the C2 KIR ligand experienced more frequently aGvHD (P = 0.03). The HLA-C1 ligand, therefore, proved to have a protective effect towards severe aGvHD. The probability of rejection increased in KIR epitope-mismatched recipient/donor pairs (P = 0.01). Finally the stage of disease at transplantation and cell dose were important for patient survival (P = 0.003, P = 0.048 respectively).
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