Absence in human milk of bovine β-lactoglobulin ingested by the mother. Unreliability of ELISA measurements

Objectives. To analyze the presence of bovine β-LG in breast milk. Methods. Human milk samples from 14 healthy non-atopic women on diets with different cow's milk contents were examined. The total concentration of β-LG immuno-like proteins (β-LGIP) was determined by enzyme linked immunosorbent assay (ELISA). Identification of antigens was done by N-terminal sequencing. Results. β-LGIP reactivity of the milk from subjects on different diets was not significantly different. Human lactoferrin, β-casein and α-lactalbumin, were identified as cross-reacting antigens. Conclusions. False-positive results in ELISA determinations of bovine β-LG In human milk might be due to cross-reactions between polyclonal antibodies and different protein antigens.