CD101 is a type I transmembrane glycoprotein, known as V7, and P126. It is a 120 kD homodimer, the member of EWI family within Ig superfamily. CD101 is found on monocytes, granulocytes, dendritic cells, a subpopulation of peripheral blood T cells and activated T cells. It has been reported that CD101 expressing Tregs posses higher inhibitory function. The biological function of CD101 is still not clear. But it has been found that BB27 antibody is able to inhibit T cell proliferative responses and this inhibitory function can be overcome by high doses of IL-2. Activation of CD101 on dendritic cells is able to induce IL-10 production.