Immunopathological changes in mice caused by Bordetella bronchiseptica and Pasteurella multocida

The immunopathological changes induced by toxigenic Pasteurella multocida, toxigenic phase I Bordetella bronchiseptica and its phase III variant were studied. Four groups of mice, each containing 21 animals, were inoculated intravenously with sublethal doses of B. bronchiseptica as follows: group 1: phase I toxigenic B. bronchiseptica whole-cell suspension (WCS); group 2: phase III B. bronchiseptica WCS; group 3: phase I B. bronchiseptica sonicated extract (SE); and group 4: phase III B. bronchiseptica SE. The fifth group received SE of toxigenic P. multocida. Lymphatic organs, lungs, livers and testes from three mice per group were examined histologically on every second day of a two-week period. In the spleen of mice, where the so-called lienotoxic effect manifested itself (groups 1, 3, 4 and 5), the percentile proportion of lymphoblasts significantly decreased in both the B and the T cell dependent areas. The lymph nodes also showed a reduction in the number of lymphoblasts. The reduction in spleen mass was partly attributable to a drastic decrease in the number of megakaryocytes and of blast cells participating in physiological extramedullary haematopoiesis in the red pulp. Opposite changes were demonstrable in group 2 the mice of which showed splenic hypertrophy.