Programmed death 1 (PD-1) activation triggers an immune checkpoint resulting in inhibition of T cells that leads to peripheral tolerance. Some PD-1 polymorphisms have been described and associated with the development of autoimmune diseases or cancer predisposition, but there are few data concerning the relevance of such polymorphisms on the clinical outcome after allogeneic hematopoietic stem cell transplant (alloHSCT). We analyzed the distribution of the SNPs PD-1.1G/A (rs36084323) and PD-1.3G/A (rs11568821) genotypes of the donor in a cohort of 1485 alloHSCT from HLA-identical sibling donors. We found an increased risk of grades II to IV graft-versus-host disease (GvHD) in patients receiving grafts from donors homozygous for the G allele at the rs36084323 SNP (P = 0.033; hazard ratio [HR] 2.2; 95% confidence interval [CI] 1.1 to 4.8) and also from donors homozygous for the A allele at the rs11568821 position (P < 0.001; HR 4.5, 95%CI 2.0 to 10.1). In contrast, the PD-1 genotype of the donor did not show association with overall survival or relapse incidence. These results suggest that the PD-1 genotype of the donor plays an important role for the development of acute GvHD after alloHSCT from HLA-identical sibling donors.

Minor histocompatibility Ags (mHags) have been implicated in the pathogenesis of GVHD after allogeneic hematopoietic stem cell transplantation (HSCT). Uridine diphospho-glucuronosyltransferase 2B17 (UGT2B17) gene deletion may act as a mHag and its association with acute GVHD (aGVHD) has been described. We retrospectively studied the clinical impact of a UGT2B17 mismatch in a cohort of 1127 patients receiving a HSCT from an HLA-identical sibling donor. UGT2B17 mismatch was present in 69 cases (6.1%). Incidence of severe aGVHD was higher in the UGT2B17 mismatched pairs (22.7% vs 14.6%), but this difference was not statistically significant (P: 0.098). We did not detect differences in chronic GVHD, overall survival, relapse-free survival, transplant-related mortality or relapse. Nevertheless, when we analyzed only those patients receiving grafts from a male donor (616 cases), aGVHD was significantly higher in the UGT2B17 mismatched group (25.1% vs 12.8%; P: 0.005) and this association was confirmed by the multivariate analysis (P: 0.043; hazard ratio: 2.16, 95% confidence interval: 1.03-4.57). Overall survival was worse for patients mismatched for UGT2B17 (P: 0.005). We conclude that UGT2B17 mismatch has a negative clinical impact in allogeneic HSCT from HLA-identical sibling donors only when a male donor is used. These results should be confirmed by other studies.

Minor histocompatibility antigen (miHA) mismatches have been related to graft-versus-host disease (GVHD) after allogeneic stem cell transplantation, but this association remains controversial due to the lack of consistency in the results obtained by different groups. The CTLA-4 genotype of the donor has been reported to be relevant in the appearance of acute GVHD. We explored the effect of the donor's CTLA-4 genotype in the incidence of acute GVHD associated with HA-1, HA-8, or H-Y miHA mismatches in a large cohort of 1295 patients receiving an allogeneic transplant from an HLA-identical sibling donor. The incidence of acute GVHD was higher if the donor and recipient were mismatched for HA-1, HA-8, or H-Y, but only when the donor had the CTLA-4 rs231775 AA genotype (hazard ratio [HR], 2.18; 95% confidence interval [CI], 1.27 to 3.75; P = .005; HR, 2.11, 95% CI, 1.06 to 4.18; P = .033; and HR, 1.50; 95% CI, 1.05 to 2.15; P = .025, respectively). In contrast, this increased risk of developing acute GVHD was not found when the donor presented the CTLA-4 rs231775 AG or GG genotypes. We conclude that the immune response to specific miHA mismatches is modulated by the CTLA-4 genotype of the donor.

Immune dysfunction in patients with multiple myeloma (MM) affects both the innate and adaptive immune system. Molecules involved in the immune checkpoint pathways are essential to determine the ability of cancer cells to escape from the immune system surveillance. However, few data are available concerning the role of these molecules in predicting the kinetics of progression of MM. We retrospectively analysed polymorphisms of CTLA4 (rs231775 and rs733618), BTLA (rs9288953), CD28 (rs3116496), PD-1 (rs36084323 and rs11568821) and LAG-3 (rs870849) genes in 239 patients with newly diagnosed MM. Patients with a CTLA4 rs231775 AA/AG genotype showed a median progression-free survival (PFS) significantly lower than those with GG genotype (32.3 months versus 96.8 months respectively; p: 0.008). The 5-year PFS rate was 25% for patients with grouped AA and AG genotype vs 55.4% for patients with GG genotype. Multivariate analysis confirmed the CTLA4 rs231775 genotype as an independent risk factor for PFS (Hazard Ratio (HR): 2.05; 95% CI: 1.0-6.2; p: 0.047). Our results suggest that the CTLA4 genotype may identify patients with earlier progression of MM. This polymorphism could potentially be used as a prognostic biomarker.