In order to select recipients without donor-specific anti-HLA antibodies, the complement-dependent cytotoxicity crossmatch (CDC-CM) was established as the standard procedure about 40 years ago. However, the interpretability of this functional assay strongly depends on the vitality of isolated donors' lymphocytes. Since the application of therapeutic antibodies for the immunosuppressive regimen falsifies the outcome of the CDC-crossmatch as a result of these antibodies' complement-activating capacity in the recipients' sera, we looked for an alternative methodical approach. We here present 27 examples of AB0 blood group-incompatible living kidney allograft recipients who, due to their treatment with the humanized chimeric monoclonal anti-CD20 antibody Rituximab, did not present valid outcomes of CDC-based pretransplant cross-matching. Additionally, four cases of posttransplant cross-matching after living kidney allografting and consequent treatment with the therapeutic anti-CD25 antibody Basiliximab (Simulect) due to acute biopsy-proven rejection episodes are presented and compared regarding CDC- and ELISA-based crossmatch outcomes. In all cases, it became evident that the classical CDC-based crossmatch was completely unfeasible for the detection of donor-specific anti-HLA antibodies, whereas ELISA-based cross-matching not requiring vital cells was not artificially affected. We conclude that ELISA-based cross-matching is a valuable tool to methodically circumvent false positive CDC-based crossmatch results in the presence of therapeutically applied antibodies.

Forty-three patients were grafted with forty-four fresh or cryopreserved allogeneic arterial vessels in order to treat infections of synthetic vascular implants as these often lead to sepsis, amputation and death. All the patients were HLA-typed whereas typing results of the post-mortem donors were inquired or genotyped from residuary vessels' segments. 84% of the patients were cured from the underlying infections with a re-infection rate of only 9% attesting this therapeutic procedure a high success rate for recovering from the bacterial infections. Since the allografts were chosen without considering HLA-histocompatibility between donors and recipients 95% of the patients developed a humoral anti-HLA immune response with 89% of them giving rise to virtually definable donor-specific antibodies. Regarding the clinical outcome 16% of the patients exhibited thromboses as the most frequent complication. In addition to clinical follow up analyses of all patients, tissue excisions of 11 patients' allografts due to various complications but not resulting from persisting infections were analyzed in order to compare these vessels' pre-and post-transplant histological appearance. In contrast to three early excised homografts (after 14 to 45 days) all of the later on explanted vessels (after 8 to 96 months) clearly showed chronic degeneration processes induced by the alloreactive immune response. Although not leading to acute graft dysfunctions comparable to those of solid organs, arbitrarily selected vessels exhibit a high degree of alloimmunization with consequent chronic degeneration processes such as the loss of smooth muscle cells. Additionally, clear signs of fibrosis of the different arterial vessel layers lead to obliterative arteriopathy and thromboses. Thus, apparently the overall practicability of the unmatched allocation of arterial homografts is clearly limited. Further approaches of arterial vessel allo-grafting are required to investigate the hypothesis that the clinical outcome of well HLA-matched homografts may lead to a significantly decreased number of thromboses.

The specification of anti-human leukocyte antigen (HLA) antibodies is an important task for patients awaiting kidney allografts. Especially the patients immunized in previous transplantations, transfusions, or pregnancies must be carefully observed, since grafting patients with HLA antigens/phenotypes recognized by their pre-formed antibodies are the main cause of harmful hyperacute and acute rejection. The complement-dependent lymphocytotoxicity-based de facto (physical) crossmatching (CDC-CM) has thus been implemented as the last diagnostic obstacle before kidney allografting. Here, an assay is performed by incubating the donors’ lymphocytes with the sera of the prospective recipients, and a negative outcome was desired for eligibility of the underlying organ allocation. Furthermore, valid antibody specification has to be performed at least quarterly for each patient on the kidney waiting list, as defined by certain guidelines, for example, the Eurotransplant guidelines. Based on the exclusion of these specificities, also referred to as virtual crossmatching, certain donors are a priori listed as unacceptable for these recipients. In this case report, we showed that defining unacceptable antigens may be difficult if the recipients’ antibodies are allele-specific after being generated in the patient who is expressing the HLA-class II antigen DQ6 and also developing antibodies against this antigen. Low resolution (two-digit) typing is used before kidney allografting. Thus, these antibodies are generally not definable, as donors and recipients share the same antigen (allelic group). Here, we demonstrate the diagnostic approaches required to exclude inadequate kidney donors for a patient exhibiting antibodies only against the HLA-DQB1*06:04 allelic variant and not against the common phenotype HLA-DQ6. In practice, the patient’s HLA-class II high resolution (four-digit) typing, as well as his antibody specification at the highest (single antigen) resolution, are included. Furthermore, we critically discuss, according to the Eurotransplant guidelines, the missing possibility to declare own HLA-antigens unacceptable, which may be very helpful for recipients who exhibit allele-specific antibodies.

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