[The vaccinal process after the intramuscular immunization of sheep with Salmonella typhimurium strain 274]

After the immunization of sheep by the intramuscular injection of S. typhimurium vaccine strain 274 the bacteria did not proliferate, but were phagocytosed and destroyed by leukocytes and macrophages; in some sheep these bacteria persisted up to day 13, inducing inflammation neither at the site of injection, nor in lymphatic nodes and internal organs. The vaccinal process in lymphoid tissue was characterized by an initial decrease in the number of lymphocytes, then a sharp rise in blast transformation, mitosis rate and the number plasmatic cells in the centers of multiplication of follicules in lymph nodes and the spleen. After day 13 gradual normalization began and by day 32 only residual manifestations of immunomorphological changes remained. In the lamina propria of the intestinal mucosa individual small macrophagal granulomas developed. The number of lymphocytes also increased in the epithelium and the lamina propria of the uterine mucosa. In the liver variations in the number of lymphocytes were observed in portal interlayers, around central veins and in the region of sinuses.