This product recognizes mouse and rat CD81, a 26kD cell surface glycoprotein that is also known as TAPA-1. In rodents CD81 is expressed at much higher levels on resting B cells than on T cells, although increased expression on T cells is found following activation.

Eat 2 induces homotypic aggregation of B cells and inhibits anti Ig and IL-4 induced proliferation. Eat 2 requires the presence of both extracellular loops of TAPA-1 for binding.