Chlamydial secretory IgA antibodies in human milk

Colostrum from 10 of 30 randomly chosen women contained IgA antibodies to Chlamydia trachomatis as shown by an enzyme-linked immunosorbent assay and a single-antigen immunofluorescence test. Specific colostral IgA was present only in seropositive women. In addition, Chlamydial-specific IgA was also detected in milk from 5 of 6 women who were shown to harbour C. trachomatis in the lower genital tract during delivery. There was a close correlation between chlamydial-specific IgA and the chlamydial secretory immunoglobulin titres in colostrum and milk samples but not between chlamydial IgA titres and the total secretory IgA content. No agreement was observed between the specific IgA antibodies in milk and corresponding serum samples. It is suggested that chlamydial-specific IgA in milk is induced by genital infections.