The Presentation of Processed, Ia Restricted, T Cell Antigenic Peptides on Antigen Presenting Cell Surfaces

Abstract

The helper T cell response to a soluble protein requires the processing of the native antigen by an antigen presenting cell (APC) to a peptide containing an antigenic determinant, which is transported to and held on the APC surface, where it is recognized by the specific T cell in the context of the appropriate Ia molecule¹. The requirement for processing and presentation of antigens for T cell recognition would not appear to apply only to T cells of the helper subset, in that recent studies have indicated that cytolytic T cells may also recognize processed forms of their antigens in the context of the MHC class I molecules. Thus, Townsend et al.² demonstrated that cytolytic T cells specific for influenza virus infected cells recognize peptides of the nucleocapsid protein which is not normally expressed in its native form on the cell surface. Furthermore, cells transfected with genes encoding a truncated soluble form of influenza virus hemagglutinin which lacks a membrane anchoring domain and consequently is not expressed on cell surfaces are, all the same, targets of hemagglutinin specific cytolytic T cells³. Thus, the ability to process and present both extracellular and intracellular proteins appears to be a general function of all cells which presumably have the machinery to anchor T cell antigenic peptides on their surfaces.