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

Objectives. To analyze the presence of bovine ?-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 ?-LG immuno-like proteins (?-LGIP) was determined by enzyme linked immunosorbent assay (ELISA). Identification of antigens was done by N-terminal sequencing. Results. ?-LGIP reactivity of the milk from subjects on different diets was not significantly different. Human lactoferrin, ?-casein and ?-lactalbumin, were identified as cross-reacting antigens. Conclusions. False-positive results in ELISA determinations of bovine ?-LG In human milk might be due to cross-reactions between polyclonal antibodies and different protein antigens.