antigen processing and presentation of peptide antigen via MHC class II peptide antigen processing and presentation via MHC class II GO:0002495 biological_process The process in which an antigen-presenting cell expresses a peptide antigen on its cell surface in association with an MHC class II protein complex. The peptide antigen is typically, but not always, processed from a whole protein. antigen processing and presentation of peptide or polysaccharide antigen via MHC class II antigen processing and presentation of peptide antigen