J.Noble HLA Human Leukocyte Antigen human MHC cell-surface proteins important in self vs.nonself distinction present peptide antigens to T cells CLASS I:A.B.C CLASS II:DR,DQ,DPHuman Leukocyte Antigen human MHC cell-surface proteins important in self vs. nonself distinction present peptide antigens to T cells CLASS I: A,B,C CLASS II: DR,DQ,DP HLA J. Noble