The antibody to AN6520 antigen, which was isolated from the liver of a patient with non-A, non-B hepatitis (NANBH), has been detected frequently in convalescent sera from patients with NANBH by the passive hemagglutination (PHA) test. In a further study, we established hybridoma cells secreting antibodies against AN6520 antigen and obtained ascitic fluids with PHA titers ranging from 1:10(5) to 1:10(7). In immunodiffusion with AN6520 antigen, all monoclonal antibodies were found to form an identical precipitin line. These lines were also identical to those formed by rabbit antiserum against AN6520 antigen and by convalescent sera from patients with NANBH. With one of the monoclonal antibodies, 1-F12, solid-phase radioimmunoassay (SP-RIA) for detecting AN6520 antigen was developed as well as blocking RIA for anti-AN6520 antibody detection. The antigen assay was 50 times more sensitive than the reverse passive hemagglutination (R-PHA) test, with a sensitivity threshold of the 1 ng/ml of antigen solution; the antibody assay was 10 times more sensitive than PHA. The results with this blocking RIA were mostly in agreement with the data obtained by PHA. Furthermore, the antigen in human sera, which had never been detected by R-PHA test, could be detected by SP-RIA.

An extract prepared from the liver of patient with chronic non-A, non-B (NANB) hepatitis was found to produce a precipitin line in immunodiffusion with a serum from a multiply transfused patient and those from patients convalescent from NANB hepatitis. The antigen was purified by gel filtration and density gradient centrifugation. The antigen had a buoyant density of 1.16-1.20 g/cm3 in cesium chloride, a sedimentation coefficient (S20,w) of 51.5, and a molecular weight of larger than 1.5 X 10(6) daltons. Electron microscopic examination revealed particles 29-34 nm in diameter (average 31.5 nm), which could be agglutinated by the specific antiserum. We developed a reverse passive hemagglutination (R-PHA) and a passive hemagglutination (PHA) technique for detection of the new antigen and antibody, respectively, and applied these to human sera. Antibody to the antigen was detected in 19/28 (67.9%) convalescent sera of NANB hepatitis. This prevalence was significantly higher than those found in convalescent sera of type A hepatitis patients (2/17 = 11.8%), type B hepatitis patients (2/15 = 13.3%), and normal blood donors (9/129 = 7.0%) (p less than 0.01); and the prevalence in hepatitis A and B patients did not differ significantly from that of normal donors. Furthermore, most (66.7%) of the cases of NANB hepatitis endemic in Shimizu City, Japan, showed clear seroconversion with respect to this antibody. These results suggest that the new antigen/antibody system is associated with NANB hepatitis.

To clarify the real situation of the spread of hepatitis virus infection due to sexual behaviour, the authers studied the prevalence of hepatitis virus markers (HAAb, HBsAg, HBsAb and HBcAb) in the sera from 204 prostitutes living in the Tokyo area. Two hundred fourty-five healthy married women whose age was comparable to that of the prostitutes served as controls.HAAb was detected in 54.9% and HBsAg in 1.9% of sera taken from the prostitutes. These rate were similar to those observed in the controls. However, HBsAb was detected in 46.5% of the prostitutes and 23.6% of the controls, and HBcAb in 44.6% of the prostitutes and 22.8% of the controls. The prevalence of these HBV associated antibodies was significantly higher in the prostitutes than in the controls. In the prostitutes, the occurrence of HBsAb and HBcAb increased with advancing age, which showed a significant difference between the younger and older age groups.These results suggest that prostitutes are a high exposure group to HBV and that HBV infection is sexually transmitted, which may support the conventional hypothesis that HBV infection in adults with mature immunity rarely develops a chronic carrier state of the virus.

Cryostat sections of the liver representing fulminant B‐viral hepatitis were investigated with antisera against human immunoglobulin G(IgG), immunoglobulin M(IgM), C3, C4, C1q, hepatitis B surface antigen (HBsAg), and T‐lymphocytes using the immunofluorescence and immunoperoxldase techniques. The liver showed positive staining for IgG, IgM, C3, C4, C1q, and HBsAg in the viable and necrotic hepatocytes and Kupffer cells in a granular fashion. Furthermore, the cell membrane of lymphocytes present in the liver were positively stained with anti T‐lymphocyte sera. The numbers of T‐lymphocytes recognized were predominant both in portal tracts and within hepatic lobules over those of non‐T‐lymphocytes. It suggests that perhaps some of the end results of fulminant hepatitis inflammatory reactions may be mediated in part by T‐lymphocytes.

A clinical and fundmental study of a new serum antigen (Arai antigen) was performed. The sera from 1,804 patients or controls was tested for the presence of the antigen by immunodiffusion. It was detected in 8 of 13 patients with fulminant hepatitis, 10 of 30 patients with primary hepatic cancer, 20 of 60 patients with hepatic cirrhosis, 10 of 69 patients with acute hepatitis and 7 of 60 patients with chronic active hepatitis. It was rarely detected in patients with nonhepatic diseases and control subjects. The difference of laboratory findings could not be found among patients with acute Arai antigen positive or negative hepatitis. Moreover, there was no correlation between Arai antigen and alpha-fetoprotein. Purified Arai antigen was confirmed to have an inhibitory effect on the E rosette formation in peripheral blood lymphocyte in vitro. These results suggest that Arai antigen is associated with hepatic diseases and may possibly regulate the immune system in vivo.