Opsonic Requirements for Bacterial Phagocytosis

Abstract

THAT specific antibody is required for the uptake of most, if not all, bacteria by phagocytic cells has been accepted since the early work on opsonins by Almroth Wright and Douglas. In recent years evidence has accumulated that complement may also be involved since partial removal of complement in a variety of phagocytic systems reduces the rate and amount of uptake^1,2. The fragments of 7S γ-globulin which can be obtained by enzymatic digestion of antibody are reported to be unable to fix complement in their combination with antigen³, and recently Miescher et al.² have found that such fragments possess little or no activity in an in vivo opsonic system. Using a highly sensitive intraperitoneal test in mice we have confirmed that papain or pepsin-digest fragments of rabbit 7S antibody aro only capable of opsonizing S. adelaide when used at a concentration one thousand times greater than the minimum effective dose of the original 7S γ-globulin. Quantitatively similar results with fragment I have recently been obtained by Shands and Suter⁹. Fragments labelled with iodine-131 were found to combine with the bacterial surface in a manner quantitatively similar to the 7S γ-globulin. This suggests to us that complement-binding on the bacterial surface may be mandatory for phagocytosis to occur.