Fifty-six serum samples from 18 cases of acute hepatitis associated with the Australia antigen have been studied. The antigen has been identified by Prince's microtechnique of immunodiffusion and by electron microscopy with minor modifications after sera centrifugation without addition of antiserum.1 After preliminary centrifugation of diluted serum in phosphate buffered saline at 4 C for 30 minutes at 3,000 rpm, the supernatant is centrifuged twice at 45,000 g for one hour. The pellet is stained with 2% phosphatidic acid at pH 6.5 and examined at a magnification of 60,000.
Several blood samples in the course of the disease were obtained until the antigen which was titrated on a two-fold dilution of sera had disappeared from the blood.
Three typical forms of Au antigen2-6 ie, the small spherical particle, the large double-coated particle, and the tubular forms (Fig 1) were seen by electron microscopy.
Five typical cases with