T Cell Assay to Track Presentation of an Influenza Hemagglutinin Epitope Presented by the MHC-II Protein HLA-DR1

Antigen presentation is a specialized function of the immune system where peptides generated from cellular or internalized proteins are presented on Major Histocompatibility Complex molecules on the surface of antigen-presenting cells for recognition by T cells. The binding of these MHC-peptide complexes to hypervariable receptors on the surface of a T cell leads to its activation. T cell activation induces increases in cell-surface activation markers such as CD69, which can be tracked by flow cytometry. Here we describe a method that uses flow cytometry and a recombinant T cell to track the presentation of an MHC-II HLA-DR1 restricted epitope generated from the influenza hemagglutinin protein.