MACROPHAGES AND THE PROTECTIVE ACTION OF BREAST MILK IN NECROTIZING ENTEROCOLITIS

Abstract

An experimental model of necrotizing enterocolitis in newborn Sprague-Dawley rats has previously been described (Barlow et al., APSA 1974). It was found that newborn rats exposed to daily hypoxia all succumbed to this disease within two to five days if fed artificial formula (F) but not if fed breast milk (BM). These studies were undertaken to determine the protective factors in BM. In vitro, BM killed 99% of 107/cc Klebsiella in two hours, while frozen breast milk (FBM) killed none and F supported bacterial growth. The Klebsiella used was one which produced peritonitis and sepsis in the experimental model. FBM and F lack the 106/cc macrophages (mØ) present in BM. FBM plus 106cc rat peritoneal mØ or rat peripheral white cells or rat BM mØ also killed these organisms in vitro. In the experimental model, all rats died if fed F, 90% died if fed FBM and 20% died if fed F plus peripheral white cells. These studies suggest the importance of the mØ in milk as cells capable of killing potential bacterial pathogens and of preventing necrotizing enterocolitis in the appropriate stressed animal.