Association of kidney graft failure with a positive flow cytometric crossmatch

We examined the pretransplant sera of 154 cadaver kidney recipients for anti‐donor antibodies against T lymphocytes using the flow cytometry technique. All patients had negative routine lymphocytotoxic crossmatches. 31 of the 154 (20%) patients were positive in the flow cytometric T‐cell crossmatch (FACS‐T‐XM). A positive FACS‐T‐XM was associated with irreversible rejection (p < 0.01 at 14 days, p < 0.001 at 30 d, p < 0.001 at 1 year). The 1‐yr graft survival rate of FACS‐T‐XM‐negative patients was 85% in contrast to 58% for FACS‐T‐XM‐positive patients (p < 0.001). 84% of the irreversible rejections in FACS‐T‐XM‐positive patients occurred within the 1st month after transplantation. These results suggest that a positive FACS‐T‐XM should be considered a contraindication for transplantation. We developed a flow cytometric assay to determine the complement‐fixing capacity of antibodies causing a positive FACS‐T‐XM. Of 14 patients who were examined, 10 had noncomplement‐fixing and 4 complement‐fixing antibodies. All 10 patients with noncomplement‐fixing antibodies experienced acute rejections, which were irreversible in 4. These results demonstrate that noncomplement‐fixing anti‐T cell antibodies, which cannot be detected in the lymphocytotoxic crossmatch assay, are clinically relevant.