919 ALTERATIONS IN IMMUNOLOGIC FACTORS IN HUMAN MILK DURING LACTATION

Abstract

The effects of the duration of lactation upon the concentrations of lactoferrin, lysozyme, total IgA, secretory IgA (SIgA), SIgA antibodies to E.coli somatic antigens and the numbers and functions of leukocytes in human milk were investigated. Milk samples were obtained from mothers 20-35 years of age during the first six months of lactation. Confounding variables such as collection and storage conditions were controlled; longitudinal and cross-sectional surveys were performed. The concentrations of phagocytes, lymphocytes, lactoferrin, total IgA and SIgA and the stimulation of lymphocytes by phytohemagglutinin decreased during the first 12 weeks and then remained unchanged for the next 12 weeks. In contrast, it was found in the longitudinal study that specific SIgA antibodies often increased during lactation (rise in reciprocal titer, mean ± SD, 10.6 ± 18.4). Furthermore, the concentrations of lysozyme, after falling to a nadir of 21-29 μg/ml at 2-4 weeks of lactation, rose progressively to 245 μg/ml at 6 months (p < 0.001). Similar levels of lysozyme were also found in human milk collected at 9 months and 1 year of lactation. Although the in vivo significance of these immunologic factors has not been ascertained, the alterations in the concentrations of these factors during lactation may be specific adaptations that protect the developing infant.