The major histocompatibility complex (MHC) is a cluster of genes that are important in the immune response to infections. In mice, this complex is referred to as the histocompatibility 2 (H-2) region. DS-MB-03943 recognizes a polymorphic epitope present on murine MHC class I molecules, which are expressed at varying levels on the majority of nucleated cells. DS-MB-03943 specifically recognizes mouse strains with the haplotypes H-2b, w16 and H-2d, p, q. Mouse strains with the haplotypes H-2f, r, s, w17, w23, w27 show weak reactivity with this antibody.