Immunological factors in breast milk in relation to allergy in mother and child

• Background: The allergy preventive effect of breast-feeding against the development of allergy is controversial and some of this controversy may be due to differences in the composition of breast milk between different mothers.Aim: To analyse IgA, cytokine and chemokines levels in human milk and relate the findings to matemal allergy and to development of atopic disease and IgA production in the infants, and furthermore, to assess the effects of breast milk on CBMC cytokine production. To approach these aims, several assays and methods had to be developed.Material and Methods: The levels of total IgA, secretory IgA and ß-lactoglobulin, ovalbumin and Fel d 1 specific IgA antibodies in breast milk and saliva, as well as IL- 4, -5, -6, -8, -10, -13, -16, IFN-γ, TGF-ß, eotaxin, MIP-1α and RANTES in breast milk were analysed by ELISA. Cytokine responses from phytohaemagglutinin, cat dander or ovalbumin stimulated cord blood mononuclear cells were studied in the absence or presence of colostrum.Results: The composition of immunological factors in breast milk varied widely between different mothers. The levels of secretory IgA and ß-lactoglobulin and ovalbumin specific IgA were higher in breast milk from non-allergic than allergic mothers. On the other hand, allergic mothers had higher levels of IL-4, IL-8 and RANTES in their breast milk. There were no relation between the levels of secretory IgA, cytokines and chemokines in breast milk and the development of atopic disease and salivary IgA production in the infants, however. Colostrum inhibited phytohaemagglutinin induced IFN-γ and IL-4 production and cat dander induced IFN-γ production. In contrast, allergen induced IL-5, IL-10 and IL-13 production was enhanced by colostrum. The effects of breast milk on cytokine production were independent of the atopic status of the mothers. The inhibiting effect of colostrum on phytohaemagglutinin induced IFN-γ production correlated with breast milk TGF-β levels, and was partly blocked by the addition of an anti-TGF-ß antibody.Conclusion: There were great individual variations regarding the levels of total and allergen specific IgA, cytokines and chemokines in human milk. Furthermore, breast milk from allergic and non-allergic mothers differed in several aspects. These differences seemed to be of minor importance for the development of atopic disease and IgA production in the breast-fed infant up to two years of age, however. The composition of human milk and the observed effects of breast milk on allergen and mitogen induced cytokine production confirms the anti-inflammatmy properties of human milk, and also suggest possible mechanisms whereby breast-feeding may protect against development of atopic disease. Our results do not support that the effects of breast-feeding are dependent on differences in the immunological composition of the milk, however.

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