ABSTRACT
A complex mixture of 10,000 fragments derived from cellular proteins is displayed on the surface of cells in association with class I glycoproteins of the major histocompatibility complex (MHC). Cytotoxic T-lymphocytes (CTL) bind to the class I molecules, sample the peptides being presented, and lyse those cells that display new antigens as a result of viral infection, tissue transplantation, autoimmune disorders, or disease states such as cancer. One copy of a foreign antigen is thought to be sufficient to stimulate an effective immune response. From 3 X I 010 cells ( 10 I of cells), the quantity of peptide present at one per copy per cell would be approximately 65 fmol. Identification of a single peptide antigen present at this level in a mixture with I 0,000 other peptides represents a daunting analytical challenge. Here we describe the use of microcapillary high-petformance liquid chromatography (HPLC) electrospray ionization (EST) mass spectrometry (MS) in conjunction with a sensitive immunological assay to characterize a minor histocompatibility antigen involved in graftversus-host disease (GVHD) associated with bone marrow transplantation (BMT) [1,21.
