So our CD four T cells can either stimulate the humoral immunity or they can stimulate the cell mediated immunity. On the other hand, as we'll see in just a moment, the CDAT cells can only stimulate the cell mediated immunity. So what exactly is a CDAT cell? Well, a CDAT cell contains that same AlphaBeta subunit, that same T cell receptor but it contains a different glycoprotein. It contains a CDA glycoprotein. And what the CDA glycoprotein does is it is able to bind to the major histocompatibility complex class one and not the class two one.