The Interaction of Leucocidin with the Cell Membrane of the Polymorphonuclear Leucocyte

Abstract

When leukocidin is incubated with leukocytes it is inactivated in solution and only a little adsorption takes place. This reaction has been used to purify the cell membrane. The interaction of the membrane with leukocidin is very complex and at least three pehnomena occur An inactivation of leukocidin in solution by large amounts of membrane which is synergistic between the two components of leukocidin, is thermolabile and is not inhibited by electrolyte. An adsorption of leukocidin which is synergistic between the two components of leukocidin, does not proceed to the sarre extent as the inactivation in solution and is a function of the phospholipid components. Phospholipids isolated from the membrane adsorb leukocidin but the adsorption requires the presence of several molecular species. Polymerization of leukocidin induced by ten-fold smaller amounts of membrane than are required to bring about the first two interactions. The polymerization is reversed by adjustment of the ionic strength. It is due to the presence of the lipid components of the membrane. Different lipids are equally effective in inducing the polymerization. Each component of leukocidin will polymerize in the absence of membranes and lose biological activity at low ionic strength. This is reversed by electrolyte and it does not proceed to the same extent as in the presence of membranes. The nature of the interaction of leukocidin with cells, membranes and lipids and the spontaneous polymerization indicate that each component of leukocidin can adopt different isomeric forms. The relationship of the interaciion with the membrane to the cytotoxic effect of leukocidin is discussed.