HLA SPECIFIC ANTIBODIES IN VASCULAR REJECTION OF RENAL ALLOGRAFTS.
          A.W. Harmer, A. Turner, C. J. Reid, R.W. Vaughan. Tissue Typing & Dept Paediatric Nephrology, Guy's Hospital, London, UK.
          A biopsy diagnosis of vascular rejection is often thought to indicate a humoral component in the rejection episode, and in some cases plasma exchange has consequently been used as a treatment for vascular rejection. The aim of this retrospective study in paediatric renal allograft recipients was to determine whether HLA specific antibodies were present at the time of a biopsy diagnosed vascular rejection episode. There were 91 cases of vascular rejection in 73 patients transplanted between 1985 and 1996. Serum samples were screened for HLA class I and class II specific antibodies by PRA-STAT. A minimum of 1 pre-transplant and at least 1 sample coincident with the rejection episode was required for inclusion in the study. In 56 of 91 cases there were sufficient samples, with a mean of 5.3 +/- 2.9 samples being tested for each rejection. There were no detectable HLA specific antibodies coincident with the rejection episode in 37 of 56 cases. Nineteen rejection episodes were accompanied by antibody production of which 12 showed specificity for donor HLA antigens. One year graft survival in patients with no antibody at the time of rejection was 62.2% and in patients with antibody was 29.4% (p=0.049). Plasma exchange was used as a treatment in 66.6% of patients with antibody but there was no significant difference in graft survival compared with those not receiving plasma exchange. Analysis of antibody titre by PRA-STAT indicated that whilst titre fell following plasma exchange there was frequent rebound within days. In conclusion the results of the study showed that biopsy diagnosed vascular rejection is not associated with HLA specific antibody production in 66% of cases studied. Those rejection episodes which were accompanied by antibody production had a poor prognosis, and in this series of retrospectively studied patients plasma exchange was not successful in the treatment of rejection episodes. Prospective testing for antibody production at the time of rejection may be of use in determining treatment strategies in the future.