Clinical relevance of major histocompatibility complex class I chain-related molecule A (MICA) antibodies in live donor renal transplantation - Indian Experience

MHC Class I Related Chain A (MICA) Antibodies - A Potential Cause of Renal Allograft Rejection

MHC class I related chain A (MICA) antibodies, especially those directed against the donor in absence of donor-specific anti-HLA antibodies have been reported to be possibly associated with renal allograft rejection in sensitized recipients. We are the first ones to present a case series of five patients who underwent primary live related donor renal transplantation in non-sensitized recipients either in the presence of donor-specific MICA antibodies (MICA-DSA) or developed de novo. Four of them presented characteristics of either accelerated, acute or chronic antibody-mediated rejection (AMR) attributable to the presence of MICA DSA. This case series emphasizes that AMR due to MICA-DSA is amenable to treatment with conventional regimens for treatment of AMR and there is a need for screening of MICA antibodies especially those directed against the donor on case to case basis.

Histologic Antibody-Mediated Kidney Allograft Rejection in the Absence of Donor Specific HLA Antibodies

Histologic antibody-mediated rejection (hAMR) is defined as a kidney allograft biopsy satisfying the first 2 Banff criteria for diagnosing antibody-mediated rejection (AMR): tissue injury and evidence of current/recent antibody interaction with the endothelium. In approximately one-half of such cases, circulating HLA donor specific antibodies (DSA) are not detectable by current methodology at the time of biopsy. Some studies indicated a better prognosis for HLA-DSA-negative cases of hAMR compared to those with detectable HLA-DSA, whereas others found equally poor survival compared to hAMR-negative cases. We reviewed the literature regarding the pathophysiology of HLA-DSA-negative hAMR. We find 3 nonmutually exclusive possibilities: 1) HLA-DSA are involved, but just not detected; 2) non-HLA DSA (allo- or autoantibodies) are pathogenically involved; and/or 3) antibody-independent NK cell activation is mediating the process through "missing self" or other activating mechanisms. These possibilities are discussed in detail. Recommendations regarding the approach to such patients are made. Clearly, more research is necessary regarding the measurement of non-HLA antibodies, recipient/donor NK cell genotyping, and the use of antibody reduction therapy or other immunosuppression in any subset of patients with HLA-DSA-negative hAMR.