SIgA is *not* digested.  It has a special J chain on it which protects
it from being digested.  SIgA participates in something called mucosal
immunity which is a whole different type of immunity than these dolts
seem to understand.  The people who say that are ignorant.  Probably
the same ones who tell mothers they cannot breastfeed if they have ITP
because the antibodies they produce against their platelets will get
into the milk and cause the baby to have ITP.  I can't stand it.

See Scientific American December 1995.

Jack Newman, MD, FRCPC