Anti-MICA Antibodies: Risk Factors For Sensitization And The Impact On Renal Transplantation Outcomes

Objective and SignificanceWith advances in surgical techniques and the emergence of new immunosuppressive drugs, Kidney transplantation has become the most effective means of treating end-stage renal disease. Acute rejection (AR) is the most frequent post-operation complication, which is one of important risk factors of losing graft function and failure of long-term survival. Rejection is divided into cellular rejection and humoral rejection,Humoral rejection plays an important role after renal transplantation. Generally, the human histocompatibility antigen (Human leucocyte antigen, HLA) antibodies (PRA) are the main humoral antibody, which are closely related renal transplantation rejection and graft survival rates. Especially in the body before transplantation recipients against donor-specific antibodies can cause hyperacute rejection. However, even the HLA genes were completely matched between recipient and donor, rejection after renal transplantation is still possible. It is recognized that some non-HLA antibodies can also be mediated humoral rejection. MIC genes across the human major histocompatibility complex 1 (MHC-I) class 2Mb length of the region, of which only MICA and MICB Coding, expression, transcription. MIC genetic encoding product structure are similar to MHC-â… class molecular structure, including 383-389 a peptide, amino acid contains three exocellular structure domain (alpha 1, alpha 2, alpha 3), and alpha 1, alpha 2 formed the antigen parts. MIC genetic code of molecules did not combination with T cell receptor (TCR), not connected with beta 2 micro globulin, nor combining peptides with related antigen processing, had nothing to do with transporter associated with antigen processing, but combination with NKG2D molecules. MICA gene were highly polymorphism, at least were found 61 alleles, which polymorphisms located mainly in the alpha 2 and alpha 3 structure domain. Classic HLA-â… molecular were widely distributed in human cells, but MICA mainly expressed in epithelial cells and fibroblasts cells, especially intestinal epithelium cells, moreover also expressed in most epithelial tumors cells (stomach cancer, colon cancer, lung, breast, kidney, and ovarian cancer, etc), played cytotoxic effects by combination with gamma, the delta T cells, CD8+T cells and the NKG2D/NK cells DAP10 receptors. MICA genes were also obviously racial specificity. The most common MICA alleles in Asian crowd were MICA*002,MICA*004,MICA*008,MICA*007,MICA*010,MICA*017å'ŒMICA*049.Major histocompatibility complex class I-related chain A antigen (MICA) as an important highly polymorphic glycoprotein antigen, is a polymorphic molecule, through the cellular and humoral immune responses. Reports have confirmed that antibody of MICA generated in immune responses had important significance with transplantation. MICA antigen may lead transplant rejection by activating the antibodies in immune mediated or cell mediated reacted role. MICA as a polymorphism antigen, can produce specific antibodies in patients with renal allograft. Anti-MICA antibodies were detected in heart, kidney and pancreas transplant recipients. Studies have confirmed that anti-MICA antibodies have some correlations with acute renal allograft rejection and chronic allograft dysfunction. Hankey detected MICA express in transplanted kidney or puncture in the pancreas by immunohistochemical method, MICA expressed in all cases of acute tubular necrosis (ATN) and acute rejection. MICA did not express in normal kidney tissues. There is a correlation between the cell damage and MICA gene expression in cell surface. However, in renal transplant recipients without HLA antibodies, the relationship between anti-MICA antibodies and renal transplantation need more attention. Some of the topics are discussed and studied in the role of anti-MICA antibodies on renal transplantation.The first part of study, analysis the sensitization factors of anti-MICA antibodies in patients with end-stage renal disease.Materials and Methods98 patients with end stage renal disease were selected in 2008.1-2008.12, which were detected anti MICA antibodies and the specificity. MICA fluorescent microspheres were given by Professor Zou Yizhou, coating antigen of MICA* 001, MICA* 002, MICA*004, MICA*007, MICA*009, MICA*012, MICA*017, MICA*018, MICA*019, and MICA*027.By Luminex flow cytometry, add serum into MICA antigens known fluorescent microspheres, then add R-phycoerythrin (PE) labeled goat anti-human IgG, resuspend fluorescent microspheres, read on Luminex machine. Using the Data Collector Versionl.7 software for data acquisition, each color laser to read the MICA antigens were> 100 microspheres, obtain PE fluorescence intensity by molecular cut-off scores and interpret of the 0,2,4,8, the OD value of≥4 as the anti-MICA antibodies, access to anti-MICA antibody specificity. According to anti-MICA antibodies, they were divided into anti-MICA antibody positive (+) group and anti-MICA antibodies (-) group. Collecting two groups of patients age, sex, primary disease, transplant history, pregnancy history, dialysis, blood transfusion, panel reactive antibody (PRA), etc. They were compared between the two groups. Reactive antibody was detected by U.S. Laimu De mixed antigen plate (LATM) and Lai Mude antigen panel (LAT). By ELISA (enzyme-linked immunosorbent assay) technique, different HLA antigen was coated inTai Saqi board, binding samples of serum with anti-HLA-IgG antibody and detecting specificity anti-HLA-IgG antibodies. Statistical Methods:Data were processed using statistical software SPSS 13.0, measurement data were compared with independent-samples t test, count data were compared withχ2 test correctionχ2 test or Fisher exact test, P<0.05 indicated significant difference.Results98 patients with end-stage renal disease,16 cases were detected anti-MICA antibody, which positive rate was 16.3%. Detecting anti-MICA antibody respectively: anti-MICA*001,002,007,012,017,018,019; anti-MICA*001; anti-MICA* 004* 009,027; anti-MICA*001; anti-MICA*001; anti-MICA*007*027; anti-MICA*019; anti-MICA*001; anti-MICA*019; anti-MICA*019; anti-MICA*019; anti-MICA*004,009,019,027; anti-MICA*019; anti-MICA*001,019; anti-MICA* 002,019; anti-MICA*019.10 cases had Anti-MICA antibodies as a single,6 cases had anti-MICA antibodies for multiple (≥2 unit). Frequency of anti-MICA*001 was 20%. Frequency of anti-MICA* 002,004,007,009 were 7%. Frequency of anti-MICA*012,017,018 were 3%.Frequency of anti-MICA*019 was 33%. Frequency of anti-MICA*027 was 10%.Anti-MICA*019 and anti-MICA*001 were common. Anti-MICA antibodies (+) group and anti-MICA antibodies (-) group, history of blood transfusion (50%vs17%, P= 0.010), transplant (38%vs11%, P= 0.021), pregnancy (55%vs19%, P= 0.036), PRA (38%vs13%, P= 0.049) had significant statistical difference (P<0.05).2 cases of anti-MICA antibody-positive patients found no blood transfusion, pregnancy, transplantation and other medical history.The second part of study, the correlation of anti-MICA antibodies and renal transplantation. Materials and Methods38 cases of with end-stage renal disease experienced renal transplantation,who also were detected anti MICA antibodies before surgery. They were divided into anti-MICA antibody positive (+) group and anti-MICA antibodies (-) group. By Luminex flow cytometry, add serum into MICA antigens known fluorescent microspheres, then add R-phycoerythrin (PE) labeled goat anti-human IgG, resuspend fluorescent microspheres and read on Luminex machine. Using the Data Collector Versionl.7 software for data acquisition, each color laser to read the MICA antigens were> 100 microspheres, obtain PE fluorescence intensity by molecular cut-off scores, interpret of the 0,2,4,8, the OD value of≥4 as the anti-MICA antibodies, access to anti-MICA antibody specificity. Collecting 38 cases of transplant recipient age, gender, transplant number, donor and recipient HLA antigen mismatch number,donor kidney cold ischemia time, immunosuppressive regimen after transplant,anti-MICA antibodies changes before and after transplantation, acute rejection (AR) occurs rate, graft function recovery time and graft survival rates, etc. They were compared between the two groups. Treatment of acute rejection:give methylprednisolone (MP) pulse therapy, the dose was 0.5 g,0.25 g,0.25 g,3 d consecutive. If no significant improvement in renal function or continue to deteriorate, use anti-CD3 monoclonal antibody (OKT3) therapy,3-5 d consecutive. Statistical Methods:Data were processed using statistical software SPSS13.0, measurement data were compared with independent-samples t test, count data were compared withχ2 test, correctionχ2 test or Fisher exact test, P<0.05 indicated significant difference.Results38 cases of renal transplant recipients,10 cases were anti-MICA antibodies (+),28 cases were anti-MICA antibodies (-).The ABO blood type were same between donor and recipient. Preoperative lymphocyte toxicity test was negative. Postoperative immunosuppressive regimen were:anti-thymocyte globulin (ATG)+tacrolimus (Tac) +mycophenolate mofetil (MMF)+prednisone (Pred). Age, sex, transplant number, cold ischemia time, donor and recipient mismatch number between the HLA-A/B/DR between two transplant recipients groups were no significant difference (P> 0.05). The incidence of acute rejection (AR) in renal transplant recipients was 15.8%, which were all successfully reversed by methylprednisolone (MP) pulse therapy.4 patients in anti-MICA antibodies (+) group had AR,2 patients in anti-MICA antibodies (-) group had AR. Between two groups the incidence of acute rejection was significant difference (40% vs7%, P= 0.031). Record urine output, blood pressure, regular testing of liver, kidney, blood, urine and blood concentration of FK506, adjust the dose of anti-rejection drugs, give nutritional support and antibiotics to prevent infection, give no-heparin or low molecular weight heparin hemodialysis when no urine or urine output<1500mL/d. Renal function in all patients were gradually returning to normal. Average of renal function recovery time was 14.6±4.7d in anti-MICA antibodies (+) group, average of renal function recovery time was 8.2±4.5d in anti-MICA antibodies (-) group, there were significant differences between the two groups (P= 0.001). Follow-up 10-24 months, in anti-MICA antibodies (-) group,1 patient failed to oral anti-rejection drug and induced regular serum creatinine progressively increasing, leading transplant nephrectomy and hemodialysis maintenance therapy; 1 patient was given renal transplant nephrectomy because of renal artery reverse and hematoma. Anti-MICA antibodies (+) group were good graft function during follow-up, no special complications. Two groups of renal graft survival rates were 93%,100%.Anti-MICA antibodies had changes in some patients before and after surgery:one case of anti-MICA antibodies was negative preoperative,while it were detected anti-MICA* 007,027 postoperative 17d.1 patient before surgery had anti-MICA*001,002,007,009,012,017,018,019, while the antibodies were anti-MICA *001,002,007,009,012,017,018,019,027 on 25d after surgery.1 patient before surgery was anti MICA antibody negative, while 14d after surgery it were detected anti-MICA*001.1 patient had anti-MICA*004,009,027 before surgery, who occurred AR after the first 5d;Given methylprednisolone (MP) pulse therapy(0.5 g,0.25 g,0.25 g).Anti-MICA antibody was detected negative on 8d and 30d after surgery; Renal function gradually improved in the first 20d; Serum creatinine level at discharge was 163umol/L; Serum creatinine level during follow-up two years fluctuated in 76-136umol/L.ConclusionsFor patients with end-stage renal disease, blood transfusion, pregnancy history and transplantation history can lead to anti-MICA antibody production. Anti-HLA antibodies and anti MICA antibodies have certain relevance. Part of anti-MICA antibody probably produced by fever, infection, inflammation and DNA injury induced, which was self-reactive antibody. Anti-MICA antibodies can act with polymorphism MICA antigens expressed on graft endothelial cell, leading renal damage. Anti-MICA antibodies were associated with the renal graft rejection and delayed graft function. Dynamically monitoring anti-MICA antibodies can be useful for assessing progression and prognosis of renal transplantation rejection. The anti-MICA antibodies(+) patients may require strict matching and more powerful immunosuppressive drugs, to prevent rejection and improve graft survival.