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. [ http://www.ncbi.nlm.nih.gov/pubmed/15531770 http://www.ncbi.nlm.nih.gov/pubmed/15771591 https://www.worldcat.org/search?q=bn%3A0781735149 ]