Evaluation of Plasma Levels of Soluble HLA-G and HLA-G Genotypes in Kidney Transplant Recipients

In the field of transplantation, expression of HLA-G, a nonclassical HLA molecule with immunosuppressive functions and limited gene polymorphism, is considered beneficial for graft acceptance; various studies have aimed to demonstrate this role in transplantation. Recently, in other clinical conditions, it has been observed that insulin resistance was associated with HLA-G14bpins/del polymorphism, the most studied regulatory polymorphism of this molecule. In the present study, plasma levels of the soluble form of HLA-G (sHLA-G) were analyzed in kidney transplant recipients (n = 103) with different HLA-G14bpins/del genotypes. In a group of 26 recipients, sHLA-G was detected before and after transplantation (1 year) to evaluate early variations. In 77 recipients, sHLA-G was detected after transplantation (3-24 years) and correlated with occurrence of long-term post-transplant morbidity (diabetes mellitus, hyperlipidemia, hypertension, obesity, etc.). Methods: Levels of sHLA-G were measured in plasma with an enzyme-linked immunosorbent assay; HLA-G14bpins/del and HLA-G+3142C>G genotypes were assessed using direct polymerase chain reaction. Results: Plasma levels of sHLA-G significantly decreased during the first year after transplantation (P =.019); no significant correlations were found with genotypes or early post-transplant events. Lower levels of sHLA-G were found in recipients with post-transplant diabetes mellitus or obesity carrying the HLA-G14bpins/ins (P =.006 and P =.003, respectively) or HLA-G+3142G/G genotypes. Conclusions: A complex modulation of HLA-G, which includes both immunologic and metabolic effects, could affect the risk for long-term post-transplant morbidity in kidney transplant recipients. Associations of HLA-G, diabetes, and obesity deserve to be investigated by deeply exploring HLA-G regulatory variants.