Antibodies eluted from acutely rejected renal allografts bind to and activate human endothelial cells.

This study was designed to investigate how antiendothelial antibodies (EAbs) are involved in acute irreversible renal graft rejection. Eluates from 25 renal allografts, lost by irreversible rejection (n = 22) and by renal vein thrombosis (controls n = 3), were tested against a panel of cultured human umbilical vein endothelial cells (HUVEC). All patients were under immunosuppression at the time of nephrectomy. EAbs binding and membrane expression of adhesion molecules ELAM-1 and VCAM-1 were analyzed by flow cytometry (FACS) and by semiquantitative RT-PCR for mRNAs coding for those molecules. The absence of anti-HLA antibodies against the donor was ascertained at transplant, and before and after nephrectomy by the negativity of specific crossmatches performed using the most sensitive techniques. EAbs eluted from eight rejected kidneys bound to HUVEC. They did not induce any cytotoxicity, but their incubation with HUVEC (4 h at 37 degrees C; 2.5 mg/ml) led to upregulation of mRNAs coding for VCAM-1 (35- to 60-fold increases) and ICAM-1 (8- to 12-fold increases) as compared with control EAbs. Membrane expression of adhesion molecules was also strikingly increased, with 80% of the cells expressing VCAM-1 and 65% expressing ELAM-1 upon incubation. EAbs were detected in eight out of nine (88.8%) eluates from kidneys lost from acute vascular rejection, but in none of the 13 (0.0%) kidneys lost from other types of rejection (p < 0.0001). We conclude that EAbs, capable of activating human endothelial cells, can be recovered from acutely rejected kidneys and may play a direct role in the pathogenesis of acute rejection.

Modulation of endothelial cell function by normal polyspecific human intravenous immunoglobulins: a possible mechanism of action in vascular diseases.

Intravenous immunoglobulin (IVIg) is increasingly used in the treatment of autoimmune and inflammatory diseases, including vasculitides and Kawasaki disease. However, the outcome of IVIg interaction with endothelial cells of the vascular bed is not clear as yet. We have investigated the effect of IVIg on the in vitro activation of human endothelial cells, as assessed by cell proliferation and reverse transcription-polymerase chain reaction-detected expression of mRNA coding for adhesion molecules (intercellular adhesion molecule-1 and vascular cellular adhesion molecule-1), chemokines (monocyte chemoattractant protein-1, macrophage colony-stimulating factor, and granulocyte-macrophage colony-stimulating factor), and proinflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6). IVIg inhibited proliferation of endothelial cells in a time-dependent manner. This effect was dependent on both Fc and F(ab')2 fragments of the immunoglobulin molecule and was fully reversible. Tumor necrosis factor-alpha and interleukin-1beta also inhibited thymidine incorporation, but to a lesser degree. IVIg had no effect on basal levels of mRNA coding for the adhesion molecules, chemokines, and proinflammatory cytokines. IVIg fully down-regulated the expression induced by tumor necrosis factor-alpha or interleukin-1beta of mRNA coding for these molecules. Thus, blockade of cellular proliferation and of cytokine-induced expression of adhesion molecules, chemokines, and cytokines may explain the therapeutic effect of IVIg in vascular and inflammatory disorders.

In vivo and in vitro optimization of depletion of IgM and IgG xenoantibodies by immunoadsorption using cell membrane proteins.

A system of immunoadsorption was developed for in vitro depletion of xenoreactive natural antibodies of classes IgG and IgM from monkey and human plasma. Porcine endothelial cell membrane proteins, platelet membrane proteins, and endothelial cells were used as affinity ligands, and cyanogen bromide-activated Sepharose 6 Fast Flow and Sepharose CL-4B gels were used for chromatography. Adsorption capacity was evaluated by means of ELISA, immunonephelometry, and cytotoxicity testing. Several consecutive adsorption-desorption cycles were performed. Different parameters influencing immunoadsorption were examined: ligand density on the column gel, adsorbent-plasma contact time, ratio of plasma volume to immunoadsorbent volume, desorption conditions, and temperature. After 2 adsorption-desorption cycles, 99% and 82 to 85% of IgG and IgM antipig antibodies were adsorbed, respectively. Furthermore, there was a 74 to 77% decrease in cytotoxicity. In vivo, we observed that after one adsorption-desorption cycle, 97% of antipig IgG antibodies and 96% of antipig IgM antibodies were adsorbed, and there was an 85% decrease in cytotoxicity. The immunoadsorption method studied and optimized in vitro and in vivo therefore efficiently depleted xenoantibodies and reduced the cytotoxicity. Thus, it can be used in xenotransplantation experiments without eliminating non-specific antibodies.

Fully and long-term xenogeneic hematopoietic chimeras created in poorly concordant rat-mouse combinations: expression of hereditary donor characteristics.

We created fully and stable xenogeneic hematopoietic chimeras in "poorly concordant" rat-mouse strain combinations defined by their high histocompatibility-antigen disparity and by the high titer of mouse-serum natural cytotoxic antibodies (NcAb) to rat donor bone marrow cells (BMC). Recipients were adult male (C57BL/6 x DBA/2)F1 (BDF1) mice, and donors of untreated BMC were adult male WAG strain rats. We tried several approaches to improve the quality and the stability of the rat-cell engraftment and to avoid the risk of graft-vs.-host reaction (GVHR). Best results were obtained when: 1) BDF1 recipients were previously thymectomized and then heavily irradiated to lower their immunocompetence; 2) irradiated recipients were implanted with a newborn BDF1 thymus, which allows maturing rat T lymphoid cells to be made tolerant to mouse antigens in vivo, which lowered the risk of GVHR; and 3) recipients were given a high number of untreated rat BMC (4-5 injections of 1.6 x 10(7) cells) to reduce the risk of rejection of rat BMC by mouse NcAb. We found that rat BMC engraftment was highly effective (75 to 100% rat hemoglobin and 100% rat IgG) and long-lasting (more than 10 months). The grafted rat cells were very tolerant toward host histocompatibility antigens but maintained all their immunological potentialities. Moreover, using the "poorly concordant" Wistar Furth (WF)-BDF1 combination, we showed that a genetically controlled characteristic of the hematopoietic system of the WF rat donor was maintained and functionally expressed in the xenogeneic environment of BDF1 mice.