Phagocytosis as a Surface Phenomenon. IV. The Minimum Size and Composition of Antigen-Antibody Complexes that can Become Phagocytized

Abstract

Given the measured interfacial free energy of the Fc tail of the IgG molecule, and the likely surface area of its extremity, it can be shown that the IgG molecule has too high a kinetic energy per cm² of contactable hydrophobic area to become phagocytized. Antigen-antibody complexes with three or more IgG molecules have a low enough kinetic energy per cm² for phagocytosis to become possible, in the absence of complement. In the presence of complement, it should be possible for complexes with at least two closely spaced IgG molecules to become phagocytized. One IgM molecule per complex should suffice to cause its phagocytosis, but only after having combined with complement. The known experimental data conform closely to these calculations.