Introduction: Patients with anti-HLA-A and –B antibodies are difficult to match and represent a possible population for inclusion in pig-to-human xenotransplantation clinical trials. Donor specific antibody negatively influences allograft outcomes and similarly, contributes to antibody mediated rejection in xenotransplantation. Clinically significant antibodies, binding blood group antigens and HLA, can provide insight to understanding antibody subsets in xenotransplantation, binding species specific glycosylation and swine leukocyte antigen (SLA). It is therefore critical to accurately test for antibody to guide patient selection and future porcine genetic modifications.

Methods: Highly sensitized patient sera, with known single HLA antigen reactivity, were selected and grouped as anti-HLA-A only, -B only, both (n= 20, 24, 12). Flow cytometric crossmatch was completed on GGTA1/CMAH/B4GalNT2 peripheral blood mononuclear cells and red blood cells to assess IgG and IgM antibody binding. Cross-reactive group patterns in human sera compared to antigens found on tested SLA.

Results: IgG antibody binding among anti-HLA-B achieved 60% of samples with minimal antibody binding (MFI<5,000) compared to only 16% of those with HLA-A only antibodies. Anti-HLA-A antibodies are found to react to porcine SLA in predicted epitope patterns. Red blood cell reactivity identify some patients have anti porcine mixed isotype IgG and IgM antibodies.

Conclusion: Flow cytometric crossmatch of PBMC is a useful tool for screening and identifying anti-SLA antibodies for the sensentized. Those patients with HLA-B antibodies have a lower frequency of binding porcine cells, with many having a negative crossmatch. Antibody binding to PBMC and red cells identify need for careful patient screening and porcine genetic engineering.Figure 1. HLA single antigen reactivity (top) matched with porcine PBMC (middle) and RBC (bottom) antibody binding separated by IgG and IgM as labeled.

CITATION INFORMATION: Martens G., Ladowski J., Butler J., Reyes L., Tector M., Tector A. Selection and Stratification of Anti-HLA-A and HLA-B Sensitized Patients in Pig-to-Human Xenotransplantation Am J Transplant. 2017;17 (suppl 3).

« Back to 2018 American Transplant Congress