Shoichi Shimotori

Three phases of phagocyte contribution to resistance against Listeria monocytogenes.

The contribution of phagocytes to protection against Listeria monocytogenes was analysed in outbred ddN mice. Most of the bacteria injected intravenously at a dose of 3 × 103 to 4 × 103 were trapped in the liver within 10 min. There was a transient 10-fold decrease in the number of bacteria by 6 h. Anti-listeria activity in the initial phase was resistant to X-irradiation but was inhibited by carrageenan, and was not influenced by immunization. The protection in this very early stage of infection seemed to be attributable to the function of fixed macrophages. Viable bacteria in the organs increased progressively but slowly from 6 h to 72 h to reach maximum numbers. Bacterial growth during this period was markedly enhanced by X-irradiation or treatment with carrageenan. Accumulation of free phagocytes seemed to suppress the bacterial growth in this phase. The number of bacteria began to decrease from day 4 and became undetectable by day 9. The suppressive effect on bacterial growth in this last phase may be dependent on immunologically activated macrophages and was reversed by X-irradiation and carrageenan. The course of local infection was similar to that of systemic infection except for the lack of initial decrease. We conclude that the course of infection with L. monocytogenes can be divided into three phases with regard to the roles of phagocytes in resistance.

Purification and partial characterization of fimbriae of Vibrio cholerae O1

Fimbriae of Vibrio cholerae O1 were purified from a strain of the classical biotype, Inaba serotype (Bgd 17), and a strain of the El Tor biotype, Ogawa serotype (K23), grown on TCG agar medium by the following procedure; homogenization of the cell suspension to detach fimbriae, ultracentrifugation to remove remaining cells and their debris, concentration of the supernatant containing fimbriae with ultrafiltration, and 20 to 40% sucrose linear gradient centrifugation of the concentrated material. The fimbriae in both preparations were flexible, long fibres readily distinguishable under the electron microscope from those of CFA/I, CFA/II seen in ETEC strains. Their structural subunit was a protein of 16 kdaltons. Fimbriae isolated from both serotypes and biotypes shared antigenic determinants.

Cellular mechanisms in the protection against infection by Listeria monocytogenes in mice.

Listeria monocytogenes, in doses of 2-0 X 10(3) to 3-0 X 10(3) viable organisms, was injected into athymic nude mice, irradiated mice and mice treated with reticuloendothelial system-blocking agents. Viable counts on liver and spleen homogenates were made at intervals after infection. In both nude mice (nu/nu) and normal littermates (nu/+) of BALB/c background, the bacteria grew rapidly for 24 h but increased only slowly thereafter, to reach a plateau of about 10(5) per organ at 72 h. In nu/+ mice, the number of viable bacteria began to decrease after 6 to 9 days, with complete elimination by day 12. In nude mice, the number of Listeria remained at a stable level of approximately 10(5) per organ during the observation period of 21 days. In lethally irradiated nu/+ mice, bacteria grew progressively and extensively to reach 10(7) per spleen and 10(9) per liver by 72 h. Bacterial growth during the first 72 h was markedly enhanced by treatment with carbon particles, dextran sulphate 500 or silica. These enhancing effects were also observed in nude mice and in AKR, C3H/He and C57BL/6 animals. We conclude that both non-immune phagocytes and T cell-dependent mechanisms contribute to the resistance of mice to Listeria infection.

T-cell-independent activation of macrophages by viable BCG in tumor-bearing mice

Abstract The effect of viable or killed BCG on the depressed bactericidal activity of macrophages in mice bearing transplantable sarcoma-180, and the relationship between macrophage activation by BCG and delayed hypersensitivity to PPD were studied. Inoculation of the tumor into outbred ddN mice markedly depressed the bactericidal activity of macrophages against Listeria monocytogenes . Pretreatment with viable BCG enhanced bactericidal activity markedly. Pretreatment with killed BCG moderately increased bactericidal activity, which was detected within a few days after treatment. Pretreatment with either viable or killed BCG induced inhibition of in vitro macrophage migration 14 days after treatment and induced a positive in vitro blastogenic response. Moreover, striking activation of macrophages was obtained in nude mice 14 days after treatment with viable BCG, although migration inhibition was not detected. These results suggest the presence of a macrophage activation mechanism independent of sensitized T lymphocytes.