Mononuclear phagocytes of mice hyperimmunized with live vaccine of Salmonella enteritidis inhibited intracellular multiplication of a virulent strain of the same organism and resisted cell degeneration caused by phagocytosis of bacteria, in the absence of antibody in cell culture medium. This was referred to as cellular immunity. According to the immune transfer and immune adherence hemagglutination technique, the cellular antibody was detectible in abdominal mononuclear phagocytes of immunized mice. The cellular antidody inhi bited the growth of a virulent strain of S. enteritidis with the aid of comlement and lysozyme, either on the nutrient agar plate or in the nonimmunized mononuclear phagocytes of normal mice. This antibody was not detectible in the serum of mice hyperimmunized with live vaccine or in themononuclar phagocytes immunized with killed vaccine of S. enteritidis. This antibody was extracted from abdominal mononuclear phagocytes of mice hyperimmunized with live vaccine and proved to bemacroglobulin by ultracentrifugal analysis