Association of MPO with the surfaces of ingested bacteria has been observed microscopically (Selvaraj RJ et al. 1978). This could be a way of directing HOCl for effective killing (Klebanoff SJ et al. 1999). MPO has been shown to bind to the surface of a number of species (Miyasaki KT et al. 1987). However, even with MPO binding, most of the H2O2 would react with unbound MPO.