Anti-CD4 monoclonal antibody, clone DD9 [FITC]

Background. We recently reported that a novel CXCR5(+)IFN-gamma(+)CD8(+) T-cell subset significantly inhibits posttransplant alloantibody production in a murine transplant model. These findings prompted the current study to investigate the association of human CD8(+) T cells with the same phenotype with the development of de novo donor-specific antibody (DSA) after kidney transplantation. Methods. In the current studies, we prospectively and serially analyzed peripheral blood CD8(+) and CD4(+) T-cell subsets and monitored for the development of de novo DSA in kidney transplant recipients during the first-year posttransplant. We report results on 95 first-time human kidney transplant recipients with 1-year follow-up. Results. Twenty-three recipients (24.2%) developed de novo DSA within 1-year posttransplant. Recipients who developed DSA had significantly lower quantities of peripheral CXCR5(+)IFN-gamma(+)CD8(+) T cells (P = 0.01) and significantly lower ratios of CXCR5(+)IFN-gamma(+)CD8(+) T cell to combined CD4(+) Th1/Th2 cell subsets (IFN-gamma(+)CD4(+) and IL-4(+)CD4(+) cells; P = 0.0001) compared to recipients who remained DSA-negative over the first-year posttransplant. Conclusions. Our data raise the possibility that human CXCR5(+)IFN-gamma(+)CD8(+) T cells are a homolog to murine CXCR5(+)IFN-gamma(+)CD8(+) T cells (termed antibody-suppressor CD8(+) T cells) and that the quantity of CXCR5(+)IFN-gamma(+)CD8(+) T cells (or the ratio of CXCR5(+)IFN-gamma(+)CD8(+) T cells to Th1/Th2 CD4(+) T cells) may identify recipients at risk for development of DSA.

Binding prediction tools are commonly used to identify peptides presented on MHC class II molecules. Recently, a wealth of data in the form of naturally eluted ligands has become available and discrepancies between ligand elution data and binding predictions have been reported. Quantitative metrics for such comparisons are currently lacking. In this study, we assessed how efficiently MHC class II binding predictions can identify naturally eluted peptides, and investigated instances with discrepancies between the two methods in detail. We found that, in general, MHC class II eluted ligands are predicted to bind to their reported restriction element with high affinity. But, for several studies reporting an increased number of ligands that were not predicted to bind, we found that the reported MHC restriction was ambiguous. Additional analyses determined that most of the ligands predicted to not bind, are predicted to bind other co-expressed MHC class II molecules. For selected alleles, we addressed discrepancies between elution data and binding predictions by experimental measurements and found that predicted and measured affinities correlate well. For DQA1*05:01/DQB1*02:01 (DQ2.5) however, binding predictions did miss several peptides that were determined experimentally to be binders. For these peptides and several known DQ2.5 binders, we determined key residues for conferring DQ2.5 binding capacity, which revealed that DQ2.5 utilizes two different binding motifs, of which only one is predicted effectively. These findings have important implications for the interpretation of ligand elution data and for the improvement of MHC class II binding predictions.