Specificity
This antibody recognises a conformational CD3 epitope minimally requiring the presence of the CD3e subunit extracellular domain as it will recognize murine 3D054.8 hybridoma cells transfected with cDNA to express the human CDe subunit lacking its cytoplasmic domain. CD3 serves as a pan T cell marker, it is expressed on the surface of over 95% of circulating human peripheral T cells. CD3 is also present on ~60-80% of thymocytes and on Purkinji cells, neurons present in the cerebellar cortex. CD3 is not expressed on B cells or NK cells. The TCR complex consists of TCR heterodimers, either a/ß or ?/d expressed in a mutually exclusive manner, analagous that seen in mice on different T cell lineages. In order for the TCR heterodimer to be expressed on the cell surface it must associate with a minimal CD3 complex. The CD3 complex itself is made up of four subunits, ?, d, e and ? responsible for effective signalling upon TCR activation, via a single or multiple, depending on the subunit, immunoreceptor tyrosine-based activation motif (ITAM) present in the CD3 subunit cytoplasmic domain (Kuhns et al. 2006, Dave et al. 1997a, Dave et al. 1997b). Mouse anti Human CD3 clone MEM-57 demonstrates a mitogenic effect on peripheral blood T cells and on the lymphoblastoid Jurkat cell line (Batista et al. 2004 Brdicková et al. 2003). Clone MEM-57 immunoprecipitates proteins of ~22 kDa and more weakly ~28 kDa. from peripheral blood T cell lysates.