Description: This MR9-4 monoclonal antibody reacts with the mouse T cell receptor (TCR) V beta 5.1/5.2 chain. Composed of an alpha and beta chain, TCR specificity is typically determined by Va, Ja, Vb, Db, and Jb gene rearrangement. The MR9-4 antibody recognizes the V beta 5.1 and 5.2 chains on T cells from mouse strains with the b haplotype of the Tcrb gene, including C57BL/6, B10, and C58/J. V beta 5.1 and 5.2 are deleted in mouse strains that express MHC Class II I-E, including Balb/c, C3H, and DBA/2. Reports also indicate that V beta 5+ T cells recognize the OVA peptide.