The Vbeta5 TCR is a variant of the TCR beta chain. It belongs to Ig superfamily and is expressed by a subset of peripheral blood T cells and some T cell clones. TCR Vbeta5 has been reported to recognize some staphylococcus bacterial superantigens. MEM-262 antibody reacts with a variant of the TCR beta chain which is expressed on HPB-ALL cells (known expressing TCR Vbeta5.3). But the subpopulation of peripheral blood T cells recognized by this antibody is reported larger than other anti-TCR Vbeta5.3 antibodies.