In the preparation of patients for renal transplantation tests of human leucocyte antigen (HLA) sensitisation are performed to detect "unacceptable" HLA antigens that, if present on donor cells, would be expected to result in a positive crossmatch. Individuals bearing such specificities may then be excluded from consideration as donors. Unexpected positive crossmatch results are sometimes obtained when a serum specificity has not been detected on screening. Failure to identify a donor relevant HLA antibody in a recipient at the time of crossmatch may result in hyperacute rejection of the graft. This report describes laboratory investigations performed after a positive crossmatch result in a live donor situation. The pattern of crossmatch results indicated that reactivity resulted from HLA class I antibody. Previously performed serum screening using a standard complement dependent cytotoxicity technique had failed to identify donor relevant antibody specificities in the recipient. Retrospective flow cytometric screening of the same serum samples identified an HLA-A24 specificity of donor relevance. The lower sensitivity of methods used for routine serum screening compared with those used for crossmatching accounts for the findings in this case. The laboratory has amended its serum screening protocol to include flow cytometric analysis.

Alloimmunization can present a virtually insurmountable barrier to kidney transplantation. Past protocols to desensitize patients using plasmapheresis and cyclophosphamide have not been broadly applied because of the fear of complications, including high rates of immunologic failure.

Fifteen patients with a positive donor-recipient cross-match were desensitized with plasmapheresis to permit live donor (LD) transplantation under newer maintenance immunosuppressants. Pretransplant the patients received plasmapheresis three times weekly for a planned maximum of six treatments, plus intravenous hyperimmune globulin, tacrolimus, mycophenolate mofetil, and prednisone. Patients who were successfully desensitized and received transplants were given 10 days of OKT3 postoperatively.

Eleven of the 15 patients became anti-human globulin cross-match-negative after one to five plasmapheresis treatments and underwent LD transplantation. Relatively low initial titers of donor-specific antibody were predictive of successful attainment of a negative cross-match. Few side effects and rejection episodes were observed. All transplant patients remain dialysis-free after 3-26 months of follow-up.

A positive cross-match is not necessarily a contraindication to LD transplantation, especially for patients with low donor-specific alloantibody titers.

Donor-recipient HLA matching was retrospectively evaluated in 111 cadaveric renal transplants using Takemoto's ten-residue model in which HLA class I antigens are clustered by crossreactive group (CREGs) on the basis of amino acid sequence homology and the sharing of a particular public epitope. The grade and type of HLA residue mismatching were correlated to posttransplant, class I donor-specific antibody production (monitored by flow cytometry crossmatch), rejection occurrence and clinical outcome during the 1st year posttransplant. In 52 patients with 0 mismatchings (MMs) we observed a low incidence of rejection (11.1%) and antibody production (11.1%) for 0 CREG MM grade, while 1 MM was enough to increase immune response against graft (rejection 35%; antibodies 30%). Moreover, a significant correlation was observed between Q144, E163, Q62 and L82/R82 epitopes and the incidence of acute rejection and antibody production ("immunogenic" residues) in patients grouped for a single residue mismatch.

Differential cross-matches have been proposed to allow immunised patients to be grafted, whereas the dogma of a global positive cross-match discarded them from renal transplantation. We report our one-center experience considering current T positive cross-match as the only contra-indication to grafting, as well as patients whose sera comprise specific anti-donor antibodies. A comprehensive characterization of the antibodies was achieved by identification of auto-antibodies and specification of IgM and IgG isotype, class I and class II specificities, as well as HLA specificities. The differential cross-match comprised an auto and an allo-cross-match, against T and B lymphocytes. Historical and current sera were analysed either untreated or after DTT-treatment, at +4 degrees C and +22 degrees C. We performed 79 renal transplantations across positive cross-matches, which were 20 historical T positive cross-matches, 26 historical B positive cross-matches and 33 current B positive cross-matches. Results and graft survival were strictly identical as those obtained in the transplantations achieved with negative cross-matches throughout the same period, especially in sensitized patients. Current positive B cell cross-matches due to IgG were associated with an increased risk for early graft failure. We conclude that differential cross-match is a safe strategy permitting immunised patients to be grafted.

The importance of certain positive crossmatches (CM+) in kidney transplantation remains controversial. Fifty consecutive kidney transplants were performed across a CM+ between Jan. 1990-April 1994. In 19 cases there was an isolated B-cell CM+ (Group I), in 24 an historic T-cell IgM CM+ (Group II) and in 7 an historic T-cell IgG CM+ (Group III). Comparing groups I:II:III: early acute rejection affected 32%, 42%, 57% of grafts; mean serum creatinine at 3 months was 166, 150, 229 umol/l (p < 0.05); 1 yr graft survival was 95 per cent, 96 per cent, 71 per cent (p = 0.09). In group III both graft losses were in the setting of an additional current B-cell CM+.

Transplantation performed in either the presence of an isolated B-cell CM+ or in the presence of an historic T-cell IgM CM+ was associated with acceptable outcomes at 1 yr. An historic T-cell IgG CM+ was confirmed as a contraindication to transplantation in most circumstances, especially when coupled with a current B-cell CM+.

Immunosensitization against the human lymphocyte antigen (HLA) is a problem in most transplant centers. It prolongs the waiting list time in addition to risk of frequent acute rejections. To avoid these problems, various pretransplantation approaches have been attempted e.g. plasmapheresis (PP). The present retrospective study reports our experience with PP in this respect over a 5 year period. Twenty-three chronic hemodialysis patients with circulating panel reactive antibodies (> or = 50%) and previous kidney graft rejections were treated with 12 PP each. In addition to this, immunosuppression with cyclophosphamide and prednisolone were administered on the first day of PP and after tapering continued until transplantation. HLA-antibodies, as measured by the panel reactive antibodies and the antibody titer, decreased from about 70% to 30% (p < 0.001) and 5 steps of titerdilution, respectively with PP and immunosuppressive drugs; Twenty-two patients were transplanted with cadaveric grafts. Eight grafts were lost due to irreversible rejection, and one due to the patient's death 2 months after transplantation. The cumulative five-year graft survival at the time of follow-up was 59%. Adequate kidney function (serum creatinine mean 150 mumol/l) was observed in all grafts (n = 3) still functioning 60 months posttransplant. We conclude that pretransplantation plasmapheresis together with immunosuppressive drugs (cyclophosphamide and prednisolone) is useful in the removal of HLA antibodies in immunized patients awaiting kidney transplantation. It can be considered a valuable approach to increase the chances of successful transplantations.

Many patients with circulating antibodies to human leucocyte antigens (anti-HLA) are highly sensitised against renal transplantation and are liable to immediate graft loss through hyperacute rejection. Our aim was to find out whether removal of anti-HLA immediately before renal transplantation prevented hyperacute graft rejection.

13 highly sensitised patients underwent cadaveric renal transplants immediately after immunoadsorption (IA) treatment to remove anti-HLA. Before IA, 12 patients had a positive crossmatch against donor cells either by cytotoxic or flow-cytometric assay; results for one patient were equivocal.

Renal biopsy samples were obtained 20 min after removal of the vascular clamps in nine patients. There was no evidence of hyperacute rejection in six of the nine patients; the other three patients showed glomerular thrombosis but no other evidence of hyperacute rejection. Two of these three grafts were functioning at 31 months of follow-up. Six episodes of acute rejection occurred in five patients during the first month after transplantation and overall there were 13 rejection episodes in nine patients. At latest follow-up (median 26 months, range 9-42), 12 of 13 patients were alive and seven of 13 grafts were surviving with a median plasma creatinine concentration of 185 mumol/L (range 106-296) in the functioning grafts. No graft was lost as a result of classic hyperacute rejection.

Immediate pretransplant IA can prevent hyperacute rejection and provide an opportunity for successful transplantation in highly sensitised patients.

Patients with preformed antibodies against HLA molecules accumulate on renal transplant waiting lists and have inferior graft survival compared with nonsensitized patients. One hundred patients were included in a program of pretransplant removal of antibodies by plasma exchange (n = 90) or immunoadsorption (n = 10) in addition to prednisolone and cyclophosphamide medication. After plasma exchange, the panel reactivity and the antibody titer were reduced in about half of the patients, and after immunoadsorption the panel reactivity fell in 6 of 10 patients. Of the 83 patients who received grafts, 17 received a graft from a living donor (LD) and 66 received a graft from a cadaver donor (CD). Patients with a positive crossmatch against their LD were included in the program and were thus grafted with a recent positive, current negative crossmatched organ. Fifteen CD graft recipients had a pretreatment positive crossmatch toward their donor. No episodes of hyperacute rejection were seen. One- and 4-year graft survival rates in LD transplants with a recent positive and current negative crossmatch were 77% and 64%, respectively. At 1 and 4 years, graft survival rates were 70% and 57% in pretreated first CD graft recipients (n = 27) and 61% and 47% in pretreated regrafted patients (n = 39), respectively. In this program, a high rate of transplantation among the sensitized patients was achieved. Graft survival was inferior to that seen in nonsensitized patients, but was comparable to graft survival in sensitized patients at other centers.