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TITRATION OF HLA CLASS I AND CLASS II ANTIBODIES USING HLA ANTIGENS BOUND TO POLYSTYRENE BEADS.
James A. Rogers BS 1, Marina Kennedy BS 1, Jason Crumpton BS 1, Bhavna Lavingia CHS 1, Albert Quan MD 2, Joseph Zhou MD 3 and Peter Stastny MD 1. 1 Internal Medicine, Univ of TX Southwestern Medical Center ; 2 Pediatrics and 3 Pathology, Univ of TX Southwestern Medical Center, Dallas, TX .
Several studies have shown that it is possible to transplant kidneys into sensitized recipients when anti-donor HLA antibodies are reduced. The challenge for the HLA lab is accurate quantitative determination of anti-HLA antibodies prior to and following transplantation. Antibody titrations with donor cells may be difficult to perform when antibodies against T cells or B cells are used to treat the recipient. An alternative approach using microspheres coupled to specific HLA antigens has been evaluated in the present studies. A highly sensitized recipient (PRA class I and class II 80-100%) was transplanted with a kidney from a living donor mismatched for HLA-A3, B65 and DR13. Flow crossmatches with donor T cells were negative, but with pronase-treated B cells strongly positive. Titration using donor B cells gave an end point of 1:64. Using DR13 single antigen beads the serum titered out at 1:64. Following plasmapheresis, CMV Ig, MMF and Rituximab (anti-CD20) the titer against DR13 was reduced to 1:16. Within 6 days after transplantation anti-A3 and A11 antibodies became detectable by single antigen beads and the titer of DR13 antibodies rose to 1:512. Acute vascular rejection was observed and C4d staining was positive. One month later, HLA-A3 antibodies were no longer detected and anti-DR13 antibodies had dropped to a titer of 1:8. Biopsy showed no evidence of cellular or humoral rejection and C4d staining was negative. We conclude that HLA-coupled microspheres provide a useful tool for titration of donor-specific antibodies to evaluate recipients undergoing therapy for reduction of anti-HLA antibodies.