Rift Valley熱Virusによるマウス病変の組織発生に関する実瞼的研究 第5篇 全篇の考按並びに結論

The Rift Valley fever virus (RVFV), when inoculated intraperitoneally in the mice, reaches the liver through the portal vein and invades the liver cells through the sinusoidal endothelium, but no elective localization of the virus in the liver can be demonstrated. The virus begins to be recovered from the liver tissue 6 hours after the inoculation. It seemed to multiply not in a stepwise increasing but in geometrical progression. There seems, however, to be no direct relation between the dose of the virus and the intensity of the lesions. The lesions of the liver in the incubation period are slight and not peculiar, while on the clinical onset of the disease a characteristic necrosis occurs abruptly. It is difficult to find any transitional type of lesions. From these findings it is most probable that the incubation period is a state, where the virus multiplies by utilizing the metabolic mechanism of the host 'cells and that the clinical symptoms appear when the balance between the speed of the virus multiplication and the metabolism of the host cells is lost. The abrupt onset is also indicated by the histochemical findings on the amount of RNA and DNA and the activity of alkaline phosphatase, which suddenly begin to decrease with the onset of the disease. The necrosis of the liver cells is of coagulation nature. The gross appearance of the liver seems to depend on two factors ; the degeneration and necrosis of the liver cells and the lesions of the capillary walls, though the former probably plays a chief role. In the "red liver" the liver cells are destroyed and the injured sinusoids are dilatated passively ; in the "white liver" the necrotic liver cells still remain in their sites. The "granular liver" shows an intermediate type of changes. The most severe lesions in the mice infected with RVFV are observed in the liver, and the lesions of the other organs are slight. In the RES, there cannot be seen any productive reaction but slight degenerative changes. With the blockade or stimulation of RES, however, the surviving period of the infected mice is prolonged and the lesions of the livers decrease in extent and grade ; it indicates that the RES plays a certain role in the infection. When the mice are injected with a formalized vaccine, the checking effect on lethality begins to appear 24 hours after the vaccination, and it increases gradually in the course of 8 days. When the vaccinated mice are challenged with active virus, allergic reactions can hardly be confirmed histologically. In short, it is noticeable that the changes of the liver of the mice infected with RVFV were chiefly of a necrotic character without exudative reactions. This is the characteristic feature of the disease, which differs from other infectious diseases in which the exudative or productive cellular reactions play an important role. Also, from the viewpoint of histogenesis, the lesions are distinguished from the simple degeneration caused with some chemicals, such as carbon tetrachloride