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).