IGA ANTIBODIES IN HUMAN-MILK - EPIDEMIOLOGIC MARKERS OF PREVIOUS INFECTIONS

The concept of an enteromammary link in secretory IgA (SIgA) antibody production was tested by hypothesising that specific SIgA antibody pro files in human milk might be an epidemiological marker for enteropatho gens in a community. Milk from three subject groups was studied: 64 Sr i Lankan women living in poor suburbs of Colombo, 20 Asian immigrant w omen domiciled in Birmingham, for a median period of five years (range 14 days- 16 years), and 75 white women living in Birmingham. An enzym e linked immunosorbent assay (ELISA) was developed for the detection a nd measurement of SIgA antibodies to a panel of 14 crude O and 10 pure lipopolysaccharide antigens of diarrhoeagenic Escherichia coli strain s well known to be endemic in the Indian subcontinent. The number of S ri Lankan and Asian immigrant women with SIgA antibodies to all 14 dia rrhoeagenic E coli antigens (except O127 in Asian women) was significa ntly higher than in the white controls. The amount of E coli O antigen specific SIgA antibody activity as a percentage of total SIgA also ga ve significantly higher median values in Sri Lankan (6%) and in Asian immigrant (4%) women than in white controls (0.7%). SIgA antibodies we re highly O serogroup specific and showed excellent concordance betwee n crude O and the corresponding purified lipopolysaccharide antigens. These results suggest that milk antibody profiles represent an epidemi ological marker of exposure to enteral pathogens. The continuing speci fic milk antibody response in Asian women who have been domiciled in t he United Kingdom for many years may indicate 'memory' in the human se cretory immune system.