Analysis of HLA-G expression in serum and biopsy samples of kidney transplant recipients

In this study, we analyzed HLA-G expression in serum and graft biopsies of renal transplant patients to find out whether there is any relationship between HLA-G and renal graft acceptance. The transplant patients were divided into two groups: those without any rejection episode (n=32) and those with acute rejection (n=33). Patient sera were collected 1 day before and at various intervals after transplantation. Soluble HLA-G (sHLA-G) in serum was determined using ELISA. In time-course experiment we found that in all patients (with and without rejection) the pre-transplantation level of sHLA-G declined in the early post-transplant period (1-2 weeks). In sera collected over 1-12 months after transplantation, a substantial increase of sHLA-G was detected in patients without rejection while no change or additional decline was observed in recipients with graft rejection. In sera collected after more than 1 year post-transplantation, sHLA-G levels increased in both groups of patients (with or without graft rejection). The time-course of serum sHLA-G antigens in patients with graft rejection was in good correlation with the course of total HLA-G mRNA determined in graft biopsy samples isolated from patients with acute rejection. We further demonstrated that serum sHLA-G values were significantly higher in patients without graft rejection than with rejection (P=0.0058). This observation supports the assumption that the increase of serum sHLA-G may contribute to allograft acceptance.