Acute humoral rejection of kidney allografts in patients with a positive flow cytometry crossmatch (FCXM)

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Abstract
The patients with a positive flow cytometry crossmatch (FCXM) are categorized as a high‐risk group causing hyperacute or accelerated acute rejection after kidney transplantation. According to the successful results of ABO‐incompatible renal transplantation, we have performed the living related transplant operations in the recipients with positive FCXM for donor T cells, but having a negative complement‐dependent lymphocytotoxic reaction test. We have followed the clinical course of 4 FCXM‐positive patients, and 2 of them have developed acute humoral rejection. We report the strategies for FCXM‐positive living kidney transplantations and the characteristics of pathological findings of acute humoral rejection in FCXM‐positive renal transplants. We have had few episodes of acute humoral rejection in ABO‐incompatible kidney transplantations under immunosuppressive regimens, including cyclophosphamide, but 2 patients of 4 with FCXM‐positive kidney transplantations developed acute humoral rejections. The differences in immunosuppressive regimen between ABO‐incompatible and FCXM‐positive kidney transplantations concern anti‐lymphocyte globulin (ALG) and splenectomy. We have not performed splenectomy and ALG administration in FCXM‐positive kidney transplantations. Severe acute rejection episodes have been experienced on post‐operative days 7 and 9 in 2 of 4 FCXM‐positive recipients. The early acute rejection episodes were clinically and pathologically diagnosed as typical humoral rejections. We have examined an immunofluorescent study to prove the diagnosis of humoral rejection in FCXM‐positive kidney transplantations; both immunoglobulin M and C3 were positive for the whole course of humoral rejection. The 2 patients with acute humoral rejection recovered after treatment with double filtration plasmapheresis or plasma exchange to remove their anti‐donor antibodies. The gold standard of success in FCXM‐positive kidney transplantations is to suppress the production and reduce the level of anti‐donor antibodies after transplant operations.