Relation between weak HLA-DR expression on human breast milk macrophages and cow milk allergy (CMA) in suckling infants

The precise role of breast milk leukocytes is unknown. We therefore studied the cellular composition of breast milk and the activation of breast milk macrophages in mothers with a cow milk-allergic infant and in those with a healthy infant. Further, we sought to determine the influence of the cellul ar composition of mother's milk on the infant's risk of developing cow milk allergy. Thirty-six asymptomatic mothers (26 with atopic constitution) who se babies had challenge-proven cow milk allergy and 24 asymptomatic mothers (17 with atopic constitution) with healthy infants were recruited. Geometr ic mean ages of the infants were 3.2 mo (95% confidence interval [CI], 2.3 to 4.4) and 2.4 mo (95% CI, 1.6 to 3.7), respectively. After separation of the fat layer, breast milk cells were incubated with fluorescein-labeled MA b to CD antigens (CD14, 45, 3, 4, 8, 19, 23, and HLA-DR) and analyzed by ho w cytometry. Breast milk samples, collected with a breast pump, were proces sed immediately. Cytospin preparations of milk samples, made after separati on of the fat layer, were stained with May-Grunwald-Giemsa and examined wit h a light microscope. HLA-DR expression on breast milk macrophages was sign ificantly lower in the mothers whose infant was allergic to cow milk, 58.3% (95% CI, 44.9 to 75.6), than in the mothers of a healthy infant, 86.9% (95 % CT, 78.7 to 96.1), p = 0.012 (ANOVA). There was also a significant differ ence in the total number of breast milk leukocytes between the mothers with an allergic child, 0.17 x 10(6)/mL (95% CI, 0.12 to 0.25), and those with a healthy child, 0.08 x 10(6)/mL (95% CI, 0.05 to 0.14), p = 0.019 (Mann-Wh itney U test). These results suggest impaired function of breast milk macro phages in mothers whose infants had cow milk allergy. They may also reflect decreased antigen presentation to the inexperienced T cells in the gut or on other mucosal surfaces of the suckling infant, leading to subsequent dev elopment of food or respiratory allergies, e.g. asthma.