In addition to its role in sensing intraluminal microbial antigens, soluble (s)CD14 may regulate immune responses by its lesser known function as a lipid carrier with possible influences in the production of fatty acid-derived eicosanoids. We investigated the interrelations of fatty acids, prostaglandin E 2 (PGE 2 ), and sCD14 and their role in infant atopic eczema during the first year of life. Serum and breast milk samples from mothers and serum samples from their infants were collected at infant's age 3 mo and analyzed for sCD14 and PGE 2 concentrations and for fatty acid compositions. The main correlation of sCD14 was with arachidonic acid (20:4n-6) (AA). Dihomo-␥-linolenic acid (20:3n-6) (DHGLA) and the ratio of n-6 to n-3 fatty acids correlated positively and docosahexaenoic acid (22:6n-3) (DHA) and sum of n-3 fatty acid negatively with PGE 2 in mother's serum and linoleic acid (LA) negatively with PGE 2 in breast milk. Soluble CD14 tended to be higher and LA, total polyunsaturated fatty acid (PUFA), and sum of n-6 fatty acids were lower in breast milk received by infants with atopic eczema compared with those without. These results suggest that fatty acids contribute to the regulation of innate and adaptive immune responses and link intraluminal exposures, mother's diet, and microbes. C haracteristic dietary habits in Western societies have constantly been linked to chronic diseases such as diabetes, cardiovascular diseases, and more recently allergic diseases. The accumulating data point to the early fetal period and infancy as the critical phase (1). Specific dietary compounds, including fatty acids and probiotics, have been exploited in the development of prophylactic and therapeutic interventions, the effects ensuing through their immunomodulatory properties (2). For the infant, the effects are drawn together by outstanding breast milk composition, providing not only nourishment but also signals for the maturation of the adaptive immune responses considered imperative with regard to the risk of diseases (3).Although the major function described for soluble (s)CD14, a pattern recognition receptor, is binding of lipopolysaccharides and thus antimicrobial host defense (4), its binding specificity is not restricted to bacteria. It also binds phospholipids, thus providing a lipid transfer system (5). This innovative function of sCD14 may prove significant, with a potential to modify immune events through phospholipid polyunsaturated fatty acids (PUFAs). Both dietary and cellular fatty acids are evidently important immune regulators via their derivative eicosanoids, particularly PGE 2 and consequent cytokine responses, as suggested in allergic disease (6). The concentration of sCD14 in breast milk has been shown to be up to 20-fold higher than in serum (7), thus providing infants with an external source of sCD14 with potential health benefits as previously observed in allergic disease (8). Experimental studies have linked sCD14 to phospholipid transport in blood (5,9) and a positive correlation be...