Ontogeny of macrophage function II. Increase of A-cell activity and decrease of phagocytic activity of peritoneal macrophages during ontogenetic development of immune responsiveness in mice

A parallelism was found between ontogenesis of murine immune responsiveness in anti-sheep erythrocyte antibody responses and that of immune-participating accessory cell (A-cell) activity of thioglycollate-stimulated peritoneal macrophages. Phagocytic activity, however, did not develop in parallel with A-cell activity. Thus, phagocytic activity was highest in neonatal mice and tended to decrease until about 2 weeks of age when A-cell activity and immune responsiveness tended to increase toward adult levels.