Acquired Immunity to Plasmodium Berghei in the White Mouse

Abstract

Using a standardized inoculum of 1 million parasites of the KBG strain of P. berghei, acquired immunity was demonstrated by reinoculation of white mice cured of a primary infection by treatment with primaquine diphosphate. Immunity was manifested by survival of the majority of animals challenged with a 2d infection after cure, whereas mortality of mice with an untreated primary infection was always 100%. Splenectomy after cure altered immunity to a challenge infection so thai a majority of the challenged animals died. Some immunity was manifest in splenectomized mice by the prolongation of survival time as compared with mice with a primary infection. The pattern of the parasitemia showed a crisis on the 4th or 5th day of the infection in both immunized and control animals. The parasitemia then rose in both groups through the 7th day, after which most of the unoperated immune mice were able to control the infection, while most of the splenectomized immune mice and all of the controls succumbed to the infection. Preliminary observations were made with paper strip electrophoresis on serums of cured challenged mice as compared with mice with a primary infection which showed a rise in the gamma fraction corresponding with immunity.