[Serum inhibition factor in acute viral hepatitis]

Sera from patients with acute viral hepatitis were found to inhibit the in vitro proliferation of normal lymphocytes induced by different mitogens and antigens. SIF interfered with the intermediate phase of mitogen induced lymphocyte activation which was defined by protein and RNA synthesis indicating that SIF acts as an antiactivator and may belong to immunoregulatory physiologic serum factors. The active moiety could be separated from immunoglobulins and other proteins by means of gel filtration, anion exchange and affinity chromatography. The major SIF activity always copurified with albumin. Evaluation of SIF in sera from patients with acute and protracted viral hepatitis may be helpful in determining the outcome of hepatitis. Thus, fall of SIF activity during acute viral hepatitis always indicated complete recovery while persistence of SIF correlated with ongoing inflammatory process and persistent viral infection.