Interleukins-6,-8 and-10 and tumor necrosis factor-alpha and its soluble receptor I in human milk at different periods of lactation

In the present study, levels of interleukins (IL-), IL-10, IL-6, IL-8 and tumor necrosis factor-a (TNF-alpha) and soluble TNF-receptor I (sTNF-RI) were measured in the whey (aqueous phase) of 55 breast milk samples of lactating mothers. These milk samples were classified according to periods of lactation into: colostrum, transitional milk and mature milk. In addition, the levels of IL-10, sTNF-RI and IL-8 were measured in milk specimens from ten lactating mothers had pre-term babies and from nine lactating allergic mothers. The levels of IL-10, sTNF-RI, IL-6, IL-8 and TNF-alpha were detected in all milk samples at different periods of lactation. The levels of these cytokines in colostrum were significantly higher than transitional milk. In mature milk, the levels of IL-6 and IL-8, were significantly lower while the levels of IL-10 and TNF-alpha were significantly higher than their levels in transitional milk. The levels of IL-6, IL-8, TNF-alpha and sTNF-RI at the first 6 months of lactation were positively correlated between each other. TNF-alpha in colostrum was negatively correlated with TNF-alpha in mature milk. Non significant changes in the levels of IL-10, IL-8 and sTNF-RI were found between full term and pre-term milk and between breast milk of allergic and non-allergic mothers except IL-8 levels were significantly higher in the allergic group. The changes of pro- and anti-inflammatory cytokines at different periods of lactation may reflect the change in the immune system of the breast and alteration in the needs of the newborn for these cytokines. The chemoattractant cytokine, IL-8, was significantly elevated in mature milk of allergic mothers. The gestational age at delivery may not have any effect on the breast milk levels of cytokines. The parity and socioeconomic conditions should be considered in such kind of study. (C) 2003 Elsevier Inc. All rights reserved.