The binding of human milk lactoferrin to immunoglobulin A.

It was recognized that in human milk some amounts of lactoferrin (LF) were naturally bound to secretory IgA (sIgA). Since not only secretory component (SC) but also LF was released from sIgA by disulfide bond cleavage, it is conceivable that LF is naturally bound to IgA as well as SC. An in vitro binding test to LF and IgA was performed and the binding was confirmed by the use of an IgA-Sepharose 4B affinity column.