Immunoglobulinscontinued Immunology Review 384
Crosses
placenta?
Role(s)
Other
IgG
Yes
Defense against
bacteria & viruses.
Neutralizes toxins.
Opsonin. Passive im-
munity in newborns.
More efficient at
precipitation than
agglutination
IgM
No
Neutralizes toxins.
Opsonin.
First Ig produced in im-
mune response. Only Ig
produced by newborn.
Most efficient Ig at ini-
tiating complement
cascade. More efficient
at agglutination than
IgG. Destroyed by
sulfhydryl compounds.
IgA
No
1st line of defense.
Patrols mucosal
surfaces. Prevents
adherence of bac-
teria and neutral-
izes toxins.
In tears, sweat,
saliva, respiratory
& GI mucosa,
breast milk.
IgD
No
May play role
in B-cell
maturation.
On surface of B
lymphs.
IgE
No
Role in allergic
rxn. Binds to
basophils & mast
cells. When 2 ad-
jacent molecules
on mast cell bind
ag, degranulation
of cell with release
of histamine &
heparin.
Type I immediate
hypersensitivity
rxn.
