Abstract
The mice which had been immunized with highly virulent live S. enteritidis acquired a strong immunity against the bacilli and could perfectly survive a challenge with intravenous injection of a highly virulent strain S. enteritidis 116-54 in a dose of 1, 000×MLD. The sera of the mice contained O and H antibodies but no demonstrable factor to prevent death due to infection. However, large mononuclear cells from liver, subcutaneous tissue and peritoneal cavity of the immunized mice exhibited an immune activity. The cells could suppress intracellular proliferation of phagocytized highly virulent bacilli and finally digested them without addition of exogenous immune sera. The activity was regarded as an expression of cellular immunity. It could be established only after contact with live bacilli.
The supernatant fluid of the culture of the immunized cells or the cellular fraction which was sedimented at 100, 000g contained a transfer agent which could transfer cellular immunity. The transfer agent was inactivated by RNase but resisted DNase or trypsin treatment. An antibody reacting to live S. enteritidis 116-54 was demonstrated in the immunized cells, even after absorption with formalin treated bacilli which contained O and H antigens. This antibody, defined as the cellular antibody, could suppress the growth of S. enteritidis 116-54 in vitro in collaboration with complement and lysozyme.
