presentation of an exogenous protein antigen to helper ( cd4+ ) t-lymphocytes by antigen presenting cells ( apc ) generally requires that the apcs degrade the native protein antigen into an immunogenic peptide , a process termed 'antigen processing ' , and that this peptide bind to a major histocompatibility complex ( mhc ) class ii molecule .
C0003315
antigen presenting cells
C0206430
antigen