Inhibition of Antibody Formation by Homologous Tissue Factors

Summary Volumes of normal mouse tissue extracts, containing 40 mg of protein, when injected intraperitoneally into mice 24 hr before the intraperitoneal injection of sheep red blood cells, significantly inhibited the production of hemolysins. Fifty per cent ammonium sulfateselectively precipitated and concentrated (2 ×) the active factor(s). Acetone precipitated the active factor(s). In control experiments, in which bovine serum albumin, bovine γ-globulin, human fibrinogen and polystyrene particles of several sizes were injected, in amounts equivalent to or greater than the effective amounts of tissue factors, little inhibition of hemolysinformation was produced. Trypsin (crystallized 0.3 mg; 1–300 1.5 mg) produced significant inhibition. Crystallized lysozyme produced significant inhibition but was somewhat less active than equivalent amounts of tissue precipitates. Tissue extracts and their precipitates produced no inhibition when injected at any time after the antigen, nor did trypsin or lysozyme. Bovine serum albumin, bovine γ-globulin and polystyrene particles sometimes produced similar insignificant amounts of inhibition when given after the antigen as before it. Normal mouse serum and 50% ammonium sulfate precipitatesof serum produced no inhibition. The inhibiting activity of tissue extracts was destroyed by exposure to 56°C but not to 37°C.