THE BIOLOGIC SIGNIFICANCE OF THE MIXED LYMPHOCYTE KIDNEY CULTURE IN HUMANS

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Abstract
The mixed lymphocyte kidney culture (MLKC) in humans has been studied in normal and abnormal clinical conditions. Human renal cortical cells were extracted by collagenase treatment from the kidneys of "normal" heart-beating cadaver organ donors (n = 13), patients with end-stage renal disease (ESRD) at pretransplant bilateral nephrectomy and splenectomy (n = 13), and from irreversibly rejected renal allografts at the time of graft nephrectomy (n = 5). Proliferation of peripheral blood T lymphocytes of 2-DR-mismatched volunteers occurred in response to kidney cortical cells extracted from each of the 3 donor categories in a reaction termed the allogeneic mixed lymphocyte kidney culture. Additionally, splenic T cells from cadavers and patients with ESRD were seen to react to their autologous kidney cells. The renal cortical cells extracted from ESRD kidneys were more stimulatory in the allogeneic and autologous MLKC responses than those extracted from "normal" cadaver kidneys even when the ESRD kidneys were 99% depleted of passenger T and B lymphocytes by treatment with monoclonal antibodies T11 and B1. In order to help define the antigens operative in the MLKC, we pretreated stimulating lymphocytes and renal cortical cells with anti-class II monoclonal antibodies. The allogeneic mixed lymphocyte reaction and MLKC were inhibited ca. 80% and 30%, respectively. The autologous MLKC was unaffected by this treatment. To further support that tissue-specific immune mechanisms were operative in the reaction, experiments were performed with infiltrating lymphocytes isolated from the ESRD kidneys, which were seen to generate a proliferative response when stimulated with autologous cortical cells. However, the response of these same infiltrating lymphocytes when stimulated with allogeneic lymphocytes (MLR), was markedly weaker than the response of the patients'' autologous spleen cells. In addition, two kidneys were obtained at rejection from recipients that had received grafts from HLA-MLR-identical sibling donors. A lymphoproliferative reaction of recipient peripheral blood T lymphocytes occurred in response to (donor) renal cortical cells, but not to donor peripheral blood lymphocytes. In contrast, infiltrating (recipient) kidney lymphocytes responded to the kidney cortical cells and to donor peripheral blood lymphocytes. Moreover, peripheral blood T lymphocytes of the HLA-identical donor responded to his own kidney cortical cells, which were isolated from the rejected recipient kidney, and did not respond to recipient peripheral blood lymphocytes. Finally, a "normal" cadaveric kidney was fortuitously available at the same time that a rejected transplant (cadaver) was being studied. The recipient and the supplier of the normal kidney were mismatched at both DR loci. Infiltrating lymphocytes from the rejected graft responded more strongly to the 2-DR-mismatched kidney cells than to the spleen cells of the same donor. In contrast, peripheral blood T lymphocytes from the recipient showed a greater response to the 2-DR-mismatched splenocytes than to the corresponding kidney cells. These results provide evidence that "tissue-specific" antigens are operative in the MLKC, with a possible biologic significance in the pathogenesis of end-stage renal disease and the loss of kidney transplants.