The effect of macrophage hydrolytic enzyme levels on the uptake and degradation of antigen and immune complexes

Macrophages isolated from the peritoneal cavity of mice stimulated with thioglycollate, methanol extraction residue of tubercle bacilli (MER), Bayol F or sodium caseinate demonstrated increased levels of acid phosphatase, β glucuronidase, cathepsin D and lysozyme as compared with unstimulated cells. Elevated enzyme levels were characteristic for the stimulant used. ¹²⁵I labeled Shigella and ¹²⁵I labeled poly L (Tyr Glu) poly L pro poly L Lys [(T,G) PRO L] were endocytosed much more slowly by stimulated macrophages. Degradation of Shigella in these stimulated cells was much faster than in unstimulated cells, while degradation of (T,G) PRO L was slower in stimulated cells than in unstimulated ones. Thus, no direct correlation between higher lysosomal enzyme levels and macrophage degradative capacity could be demonstrated. Immune complexes were engulfed by unstimulated and stimulated macrophages much faster than were uncomplexed antigens (Ags), while their degradation was generally slower than that of the Ag alone.