Phagocytic potential of macrophages from within delayed hypersensitivity-mediated granulomata

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Abstract
The phagocytic potential of macrophages from within granulomas associated with delayed hypersensitivity was studied in guinea pigs sensitized with FCA [Freund''s complete adjuvant] and challenged with PDD [purified protein derivative] or live Mycobacterium tuberculosis. The results show that FCA treatment induces a 30% increase in phagocytosis of Ig[immunoglobulin]G coated erythrocytes by macrophages which migrate into a foreign body granuloma. PPD treatment enhances this index to about 70%. When live M. tuberculosis was used as antigen the phagocytic index of macrophages from lesions induced in sensitized animals was about 50% higher than in controls. The increase in phagocytosis by macrophages was maximal at 4 days and decreased 8 and 16 days after challenge, in sensitized and non-sensitized animals. In granulomas associated with delayed hypersensitivity, macrophages have a transitory increase in their phagocytic activity. Later the older cells in the center of the granuloma lose this property, thereby facilitating antigen persistence and chronicity.