In vitro studies of group E streptococci in swine leukocytes. II. Phagocytic and bactericidal properties of macrophages from immune and nonimmune swine.

Macrophages collected from susceptible swine and grown in nonimmune serum phagocytized and digested group E Streptococci (GES). However, macrophages collected from immune swine and grown in nonimmune serum were capable of much higher rates of phagocytosis and intracellular digestion of the organism. The addition of immune serum to cultures of immune macrophages increased the rate of phagocytosis but not the rate of intracellular digestion of GES by the macrophages. These findings are discussed in relation to mechanisms of cellular immunity.