The RM4-5 monoclonal antibody reacts with the mouse CD4 molecule,
a 55 kDa cell surface receptor expressed by a majority of thymocytes,
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 protein tyrosine
kinase p56lck through its cytoplasmic tail. Binding of RM4-5 is blocked by GK1.5.