Characterization, quantification, and assessment of immune protection potential of secretory immunoglobulin A in colostrum samples from Saudi women.

OBJECTIVE To characterize, quantify, and assess the function of colostral secretory immunoglobulin A (sIgA) in Saudi women. METHODS This prospective study was performed between March 2009 and February 2010 at King Khalid University Hospital, Riyadh, Saudi Arabia. Twenty milliliters of colostrum sample was collected from each of 23 healthy Saudi women (mean age 26+/-4 years) included in the study within 48 hours postpartum. Levels of sIgA and sIgM were determined by enzyme-linked immunosorbent assay (ELISA) and purification of secretory antibodies from pooled clarified sample was performed by thiophilic-gel chromatography, Jacalin-agarose chromatography, and Sephacryl S-300 gel filtration. Antibody induced respiratory burst in peripheral blood neutrophils and monocytes was assessed by chemiluminescence. RESULTS The median concentration of sIgA1 was 0.053 mg/ml, sIgA2 0.047 mg/ml and sIgM 0.067 mg/ml with interquartile ranges of 0.308, 0.158 and 0.150. The levels of antibodies were no different. Whereas, 60% of IgA1 was present in dimeric and 30% in trimeric form; the major bulk of sIgA2 (85%) were comprised of the dimeric form. Both sIgA and serum IgA were able to induce effective and almost identical respiratory bursts in neutrophils and monocytes. CONCLUSION Dimeric forms of sIgA were the predominant antibodies in colostrum samples and sIgA antibodies exhibited functional similarity with serum IgA.