Relations between the Endohistiocytic forms of Plasmodium Gallinaceum and the Immunological Course of the Infection in Fowls Inoculated with Infected Brain Tissue
Summary and Conclusions 1. The faculty of P. gallinaceum for invading both endothelial and red cells was continuously maintained for at least 19 passages in serial infections of fowls obtained by the inoculation of brain tissue containing endohistiocytic forms. 2. Endohistiocytic parasites in the brain endothelium of fowls so inoculated are observable only transitorially between the 8th and the 25th day after inoculation, with the highest percentage of positive results between the 13th and the 17th. No reappearance of endohistiocytic forms occurred in the following unmodified course of the infection (observations from the 26th day to the 80th). 3. The reinoculation of endohistiocytic forms in fowls which previously had had an endohistiocytic localization did not produce it again. 4. Splenectomy produces relapses in the blood, but does not produce the reappearance of endohistiocytic forms. Endohistiocytic forms are not produced even in the case of continuous persistence of the parasites in the blood for more than 11 days. 5. Reinoculation of endohistiocytic forms after splenectomy does not cause the reappearance of endohistiocytic parasites in the brain capillaries. 6. The conclusion is justified that an immunological process stops the first invasion of the endothelial system within 25 days after inoculation. Subsequently the endothelial cells become resistant to new invasions by parasites; neither splenectomy, nor a new inoculation of endohistiocytic forms, before or after splenectomy, can bring about a new endohistiocytic invasion. After the 25th day the infection is confined to the forms located inside red cells, and these latter only show active multiplication when a lower immunity level is produced by splenectomy.