Calculating the efficiency of direct MHC class I antigen presentation of a model antigen in a lymphoblastoid cell line (APP5P.110)

Abstract

Abstract The direct MHC class I antigen presentation pathway presents endogenous peptides at the cell surface, allowing the body to mount a CD8+ T cell response in order to eliminate diseased or damaged cells. In order to target this pathway for disease treatment, we must first understand the efficiency of antigen presentation, or the number of proteins that must be degraded in order to present one peptide-MHC complex at the cell surface. Previous studies have primarily examined the efficiency of proteins produced by infectious agents with values ranging from 0.03%-25. In this study, we investigated antigen presentation efficiency of different recombinant fusion proteins expressed in a human lymphoblastoid cell line expressed as self-proteins. These proteins are composed of a destabilization domain, an antigenic peptide that is presented on MHC class I HLA-A2 molecules, and a fluorescent reporter. We calculated the efficiency of antigen presentation in JY cells to be 0.35%. This value is considerably lower than what was previously observed with similar constructs in murine EL4 cells. We also found that treatment of the cells with either TLR agonists or IFNg, which have both been shown to increase MHC class I expression, did not alter the efficiency of antigen presentation. These findings suggest that the efficiency of MHC class I antigen presentation may be mechanistically distinct from common immune signaling pathways.