Description: The RM4-4 monoclonal antibody reacts with the mouse CD4 molecule, a 55 kDa cell surface receptor expressed by the majority of thymocytes, a subpopulation of mature T cells and dendritic cells. CD4 binds to MHC class II on the surface of antigen presenting cells and plays an important role both in T cell development and in optimal functioning of mature T cells. In T cells, CD4 associates with the protein tyrosine kinase lck through its cytoplasmic tail. Binding of RM4-4 does not block binding of the CD4 monoclonal antibodies RM4-5 or GK1.5.