Expression of HLA-G transcripts in graft biopsy samples of renal transplant recipients.

BACKGROUND

The HLA-G molecule has a high potential to modulate immune response towards the improvement of graft survival after transplantation. In this work, we have analyzed the total HLA-G mRNA expression in graft tissues of dysfunctional transplanted kidneys.

MATERIAL AND METHODS

We examined 84 kidney biopsy samples obtained from 65 renal transplant recipients with dysfunctional graft (50 males, 15 females; average age 46.8 ± 11.9 years). 52 specimens were with signs of acute rejection and 32 without any rejection characteristics (diagnosed as glomerulonephritis, ATN and IFTA). Patients with acute rejection were divided into three groups: antibody-mediated rejection (AMR; n = 23), T cell mediated rejection (TCMR; n = 16) and combined antibody and T cell-mediated rejection (AMR + TCMR; n=13). The biopsy samples were taken from a dysfunctional graft at different time periods after kidney transplantation. The relative expression of total HLA-G mRNA in biopsy specimens was determined by real time RT-PCR. The correlation between HLA-G mRNA expression and dysfunctional graft state was investigated. The impact of different factors (post-transplantation interval, gender,mismatch, induction therapy and cold ischemia time) on relative expression of total HLA-G mRNA was also studied.

RESULTS

We have found that the levels of HLA-G transcripts in kidneys with rejection were higher than those in non-rejected but dysfunctional grafts (P = 0.0003). The highest levels of HLA-G mRNA were detected at combined AMR + TCMR rejection (P= 0.005). The time-course analysis of total HLA-G mRNA expression was also studied. In both dysfunctional graft groups (rejected and non-rejected) the lower levels of HLA-G transcripts were detected during early post-transplant period (1–3 months), however a substantial increase of HLA-G mRNA expression was observed after an extended period of time(N3 months). It was also revealed that antibody induction therapy may reduce HLA-G expression (P=0.0004) and in female samples were higher levels of HLAG transcripts than those in male recipients (P=0.003). It was found no significant impact of age, cold ischemic time, PRA (Panel Reactive Antibody) score, and a number of HLA-mismatches on HLA-G mRNA expression.

CONCLUSIONS

We have demonstrated that the expression of total HLA-GmRNA in renal grafts can be influenced by different factors such as clinical state of transplanted kidney, elapsed time after transplantation, gender and antibody induction therapy. We have proved that HLA-G mRNA expression was significantly higher in recipients with acute rejection in comparison to patients with dysfunctional but non-rejected grafts.