Immunoglobulin A protects the bodys mucosal surface
s from infection and in secretions, it is found as a dimer (400 kD) joined by a short J chain and linked to a secretory portion or transport piece. In serum
found as a monomer (170 kD).
Immunoglobulin A is the main mechanism for providing local immunity
against infections in the gut or respiratory tract and may act by reducing the binding between an immunoglobulin A
coated micro organism and a host epithelial cell
. Present in human colostrum
but not transferred across the placenta
. Have heavy chains.
source: online medical dictionary: http://www.graylab.ac.uk/