The donor genotype HLA-A*02:30 matches exactly with patient BB. Patients AC, CF, DA, and EG are mismatched in one field (*01 instead of *02, *03 instead of *30, and *01 instead of *02, and *02 instead of *30, respectively) The donor genotype HLA-B*51:13 matches again with patient BB. Patients AC, CF, DA, and EG are again mismatched in one field (*57 instead of *51, *07 instead of *13, *37 instead of *51, and *51 instead of *13, respectively). The donor genotype HLA – Cw*15:06 is not an exact match to any patient, as each has one mismatch: AC with *01 in field one, BB with *14 instead of *15 in field one, CF with *07 in field 2, DA with *06 in field 1, and EG with a mismatch in both fields. In HLA class II, the donor possesses HLA- DRB1*11:07, an exact match with patient BB. The other patients all have a single mismatch in this gene. Patient AC has *07 in field 1, CF has *04 in field 2, DA has *10 in field 1, and EG has *11 in field 2. Finally, the donor genotype HLA-DQB1*0301-02 is an exact match with patient BB. The others again have a single mismatch. Patient AC has *0303 in field 1, CF *0302 in field 2, DA *05 in field 1, and EG *0301 in field 2.
Patient BB is the best choice as the recipient of this kidney, as 90% of the HLA matches were exact. The only difference between the donor and patient BB was seen in HLA-Cw where the donor genotype is HLA-Cw*15:06 and patient BB is *14:06. While a 10/10 match is ideal, a patient who is a 9/10 match with the donor can still be transplanted with success. The other patients have way too many mismatches with the donor to have a successful match. In fact, these should not even be attempted, as hyperacute rejection is absolutely inevitable in these situations.
HLA sensitization arises due to antibodies against a non-self HLA. These antibodies therefore attack HLA molecules of a donor. Anti-HLA antibodies can be acquired through blood transfusion or organ donation, sensitizing a potential recipient. This patient with kidney disease has likely received blood transfusions in the past, either for surgery (like creating a fistula) or to treat severe anemia as a result of chronic kidney disease. This donor may have anti-HLA antibodies that were passed to the recipient in the transfusion process. It is unlikely that they have another transplanted organ, but this would also be a possible way to be sensitized.
DA is not a match to receive this kidney. Because HLA-typing would be mismatched, a hyper acute rejection would occur. Hyperacute rejection occurs due to a mismatch in antibody testing prior to transplantation. The rejection occurs within 48 hours due to near-immediate ischemia and necrosis of the kidney. This can occur as early as intraoperatively. The preformed antibodies attack the donor organ. While there is some overlap in the timing of the different types of rejection, the major difference is from a histopathologic standpoint. Acute rejection can occur within weeks to months and chronic rejection within months to years. An acute and chronic rejection are both T-cell mediated processes. The acute rejection shows leukocytic infiltration of the vessels of the donated kidney as the T-cell attacks the foreign MHC. In chronic rejection, the T-cells attack a foreign MHC that resembles the self MHC carrying an antigen. On histology, thickening of the intimate of graft vessels and fibrosis of the vessels will be seen. Grossly, this causes atrophy of the organ.
In order to prevent a hyperacute reaction, antibodies are tested for in both the recipient and the donor. If mismatching occurs pre-transplantation, an immediate rejection can arise due to incompatibility. This is rare because of thorough matching beforehand. A few days after surgery, immune response from the donor can occur. To prevent this, immunosuppressive drugs are initiated in transplant patients. This suppresses the immune system’s normal response to foreign pathogens, preventing attack of the new organ. The medications reduce antibody and T-cell production. The patient typically stays on this medication long-term to prevent chronic or gradual rejection over time. The patient must maintain proper follow-up and testing to be sure that the body is accepting the transplant, the medications are working without extreme toxicity, and no chronic rejection is occurring.