PIP: The AIDS Surveillance System in Japan was set up in 1984 and by 1987, 29 AIDS patients had been reported. 10 were homosexuals, 16 were hemophiliacs and 3 were heterosexuals. 9 out of 16 hemophiliacs with AIDS had A-type hemophilia. 2 females were also reported as victims of AIDS. 19 patients have died 5 male homosexuals (4.4%) out of 113 (93 Japanese and 20 Foreigners) individuals were anti-HIV-positive. In 1984 sera from 65 hemophiliacs, 85 hemodialysis patients and 304 healthy volunteer blood donors were examined and 10 (15.4%) of the hemophiliacs proved to be anti-HIV positive. On the other hand, in Tokyo and Nagasaki 50-60% were positive, but in Tottori and Osaka only 25-28% were positive. The enzyme-linked immunosorbent assay (ELISA) test is widely used to detect antibodies, however, the test often gives false-positive reactions, and the blood must be reexamined by means of the Western-blot test or IF method. Therefore, a simple particle agglutination (FA) assay was developed by the authors using gelatin beads as the artificial antigen carrier. This assay is extremely sensitive as compared to IF and ELISA. Among HTLV-1/ATLV-carrying T-cell lines, all except one (TCL-As) were susceptible to HIV infection and showed cytopathic effect (CPE). HIV has quite a broad host range in vivo and in vitro. HIV was detected in brain macrophages from AIDS patients with encephalopathy. HIV may also infect nerve cells or glial cells. The MT-4 cell line was found to be most prone to HIV infection. In order to evaluate the virus-induced CPE of infected MT-4 cells, the H-thymidine incorporation method (cell proliferation assay) was developed that involved that involves measuring the survival of the cells. Inhibition of DNA synthesis in infected MT-4 cells was detected by this assay when the CPE was observed microscopically. This assay system is also useful for measuring the amount of infectious virus. Many chemicophysical agents such as suramin, antimoniotungstate (HFA-23), phosophonoformic acid, ribavirin, 3-azido-3-deoxythymidine (AZT) have suppressive effects on the replication of HIV in vitro. Glycyrrhizin administration was responsible 1 or improvement of immune function in 6 of 7 asymptomatic HIV carriers. Prostaglandin E2 (PGE2) and 12-0-tetradecanoylphorbol-13- acetate (TPA) were found to enhance the production of HIV significantly in infected MT-4 cells. The cell proliferation assay is used for the mass screening of neutralizing antibodies whose presence in the sera from 21 patients with AIDS, 10 individuals with ARC, 20 healthy male homosexuals and 10 healthy males was examined. The assay was sensitive enough to detect neutralizing antibodies up to a dilution of 1:10 thousand. The system using MT-4 cells seems to be suited for this purpose.