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DIFFERENCES IN THE RESPONSE TO TREATMENT OF ANTIBODIES BY HLA CLASS SPECIFICITY.
Mary S. Leffell, PhD, Robert A. Montgomery, MD,PhD, Chris Simpkins, MD, Julie A. Graziani and Andrea A. Zachary, PhD. Baltimore MD, USA, Johns Hopkins University School of Medicine, 21205, Depts. of Medicine and Surgery.

We have treated 75 patients with known antibody to donor HLA (DSA) with plasmapheresis and CMVIg. Previously, we showed that ~90% of patients followed ≥ 2 months had lost DSA while <25% of these patients had lost Ab to third party HLA and that the number of treatments needed correlated best with crossmatch titer. We examined patients according to Ab specificity (cI only, cII only, or both) to determine if specificity correlated with rejection or with number of treatments needed post-transplant. Among 66 patients with biopsy confirmation of rejection status, there was no significant difference in rejection according to antibody specificity. There was also no significant difference in the number of treatments needed to clear DSA among 50 patients who totally cleared their DSA. However, the number of treatments required did not correlate with the frequency of CDC+ crossmatches or with the mean titer. Despite a significantly lower mean titer, similar numbers of treatments were required to clear antibodies with class II specificity. These data suggest a greater difficulty in eliminating cII-specific antibodies. Lower expression of class II antigens and/or route of antigen presentation may contribute to differences in down regulation.

DSA Specificityc I onlyc II onlyboth c I and c II
Rejection171614χ2 = 2.28
Rejection-free6103P = 0.32
Mean post-TX Treatments (n=50)9.1 + 7.89.1 + 7.09.0 + 5.4ns - all comparisons
%CDC+ (n=50)25818.2
Mean titer (n=50)24.3 + 61.01.1 + 4.03.4 + 9.3c I only v.s. c II only, P=0.04