Major histocompatibility complex (MHC) class II molecules are heterodimeric transmembrane glycoproteins that are expressed on the surface of antigen-presenting cells such as dendritic cells， macrophages， and B cells. The M5/114.15.2 antibody detects polymorphic determinants present on B cells， monocytes， macrophages， dendritic cells， and activated T lymphocytes from mice carrying the H-2b， H-2d， H-2q， H-2p， H-2r and H-2u haplotypes but not from mice carrying the H-2s or H-2f haplotypes (PMID: 6170707). This antibody recognizes both I-A and I-E subregion-encoded Ia glycoproteins (I-Ab， I-Ad， I-Aq， I-Ed， I-Ek， not I-Af， I-Ak， or I-As). M5/114 mAb is reported to inhibit I-A subregion-restricted T cell responses of the H-2b， H-2d， H-2q， H-2u but not the H-2f， H-2k， H-2s haplotypes (PMID: 6173436).