Human leukocyte antigen-G expression after kidney transplantation is associated with a reduced incidence of rejection.
HLA-G is a non-classic Human Leukocyte Antigen (HLA-G) Class I of low polymorphism and restricted tissue distribution that displays tolerogenic functions. In heart transplantation and in combined liver/renal allograft transplantation, the expression of HLA-G has been associated with a lower incidence of acute graft rejection episodes and absence of chronic dysfunction. Since the expression of HLA-G in renal biopsies has been investigated only in few patients who received a combined kidney and liver transplant, in this study we performed a cross-sectional study, systematically comparing the expression of HLA-G in post-transplanted renal grafts, stratifying patients according to the presence or absence of rejection.


METHODS
Seventy-three renal specimens (10 with acute rejection and 13 with chronic allograft nephropathy, and 50 with no signs of rejection) were immunohistochemically evaluated for HLA-G expression.


RESULTS
In the group as a whole, HLA-G molecules were detected in 40 cases (54.8%). Among specimens that presented HLA-G expression, 2 out of 40 (5%) exhibited acute rejection, 2 (5%) exhibited chronic allograft nephropathy, and the remaining 36 (90%) exhibited no signs of rejection. The comparison between patients with rejection and those without rejection showed that the expression of HLA-G was significantly increased in specimens exhibiting no signs of rejection (p<0.0001). Considering only patients with acute rejection, 8 out of 10 patients showed no HLA-G expression in their kidney biopsies when compared to patients exhibiting no signs of rejection and absence of HLA-G was observed in 14 out of 50 (p=0.0032). Similarly, considering only patients with chronic allograft nephropathy, absence of HLA-G expression was observed in 11 out of 13 specimens, whereas in patients without rejection absence of HLA-G was observed in 14 out of 50 (p=0.003). Therapy with tacrolimus was significantly associated with the expression of HLA-G and a better graft prognosis.


CONCLUSIONS
Our results suggest that HLA-G expression in the kidney allograft and the use of tacrolimus are associated with a lower frequency of acute renal rejection and chronic allograft nephropathy.
D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006084:Graft Rejection / Q000097:blood / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D006680:HLA Antigens / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics*; D006801:Humans; D015994:Incidence; D016030:Kidney Transplantation / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I