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To fully characterize human glutamic acid decarboxylase (GAD)65 protein T-cell epitopes associated with insulin-dependent diabetes mellitus (IDDM), CTL clones specific to GAD65 protein antigens were isolated from two congenital rubella syndrome (CRS)-associated IDDM patients. Overlapping nonamer T-cell epitopes recognized by both CD4 + or CD8 + CTL clones within peptides GAD65(252-266) and GAD65(274-286) were identified as sequences bounded by GAD65(255-266) with 6/9 overlapping residues, and GAD65(276-285) with 8/9 overlapping residues, respectively, using two panels of overlapping peptide analogs in cytotoxicity assays. HLA restrictive elements of the T-cell clones were also identified using a panel of B cell lines with different HLA phenotypes as targets in cytotoxicity assays. The antigenic GAD65 peptides elicited cytotoxic responses of peptide-specific CD4 + T-cell clones in the context of HLA DRB1∗0404. The CD8 + T-cell clone specific to GAD65(255-263) was found to be restricted by HLA A3 and A11. Similarly, the CD8 + T-cell clone specific to GAD65(277-285) killed peptide-sensitized target cells expressing HLA B35 and B15. The observed HLA restriction of these overlapping epitopes implies that a tandem of [DRB1∗0404-A11(3)] and/or a tandem of [DRB1∗0404-B35(15)] might predispose CRS patients to development of IDDM.

Aim Implementation of the virtual crossmatch should aid redistribution of organs to sensitized individuals. However the number of organ offers falls rapidly with increasing cPRA. Thus, additional strategies to improve transplantation rate of highly sensitized individuals are warranted. A 49 year old Hispanic woman with ESRD from DMII/hypertension and no sensitizing events showed: HLA genotype A33 68, B7 51, Cw15 15, DR8 14 52, DQ4 7; cPRA of 100% by single antigen (SA) bead testing; and autoantibody to Cw15 and DR8,14,52. The patient was listed in UNOS with cPRA 100% on 7-21-10. Methods Additional flow crossmatching and HLA antibody testing to refine virtual crossmatch information in UNOS was performed to facilitate organ offers. Results SA results were reproducible over time and confirmed by the vendor laboratory, while testing using different reagents showed no antibody to HLA class II. The flow auto crossmatch and allo crossmatches against six surrogate donors with predictive DSA based on the SA findings (DR1,4,7,9,11,13,14,15,51,52,53) were negative. Using a MFI cutoff of 10,000 based on these results the patient’s cPRA was readjusted in UNOS to 4%. She was transplanted 7-30-13 with deceased-donor kidney (HLA A3 B35,61 C4,10 DR8,17, R52 DQ2,4). Delayed graft function requiring intermittent dialysis x5 occurred post-op. No increase in DSA by SA was noted post-transplant. She required readmission once with septic shock thought secondary to ischemic colitis. Creatinine eventually reached a nadir of 0.8 mg/dl. Conclusions This case illustrates variability in the performance of standard assays to evaluate the presence and clinical significance of DSA and the need to supplement these assays.

An HLA-A3-like supertype (minimally comprised of products from the HLA class I alleles A3, A11, A31, A*3301, and A*6801) has been defined on the basis of (a) structural similarities in the antigen-binding groove, (b) shared main anchor peptide-binding motifs, (c) the identification of peptides cross-reacting with most or all of these molecules, and (d) the definition of an A3-like supermotif that efficiently predicts highly cross-reactive peptides. Detailed secondary anchor maps for A3, A11, A31, A*3301, and A*6801 are also described. The biologic relevance of the A3-like supertype is indicated by the fact that high frequencies of the A3-like supertype alleles are conserved in all major ethnic groups. Because A3-like supertype alleles are found in most major HLA evolutionary lineages, possibly a reflection of common ancestry, the A3-like supermotif might in fact represent a primeval human HLA class I peptide-binding specificity. It is also possible that these phenomena might be related to optimal exploitation of the peptide specificity by human TAP molecules. The grouping of HLA alleles into supertypes on the basis of their overlapping peptide-binding repertoires represents an alternative to serologic or phylogenetic classification.