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immunoglobulin δ chain 369 immunoglobulin ε chain
by B cells in this X-linked recessive immunodeficiency
syndrome are IgM and IgD.
S
S
S
S
S
S
S
S
+H 3 N
C H 2
immunoglobulin chain
A 64-kDa, 500-amino acid residue, heavy polypeptide
chain consisting of one variable region designated V H and
a three-domain (designated C H1, C H2, and C H3) constant
region. Human δ chains also have a 58-amino acid residue
hinge region. Two exons encode the hinge region. IgD is
very susceptible to the action of proteolytic enzymes at its
hinge region. Two separate exons encode the membrane
+H3N NH+ V 3
H
V L
L Chain
H Chain
C L
C H 3
S S
H Chain
C H 1
S S
S S
– OOC COO –
H Chain
S S
H Chain
L Chain
Variable heavy (V H) and light (V L) chain regions on an antibody.
Domains
Domain structures of light and heavy polypeptide chains, the subunits of
immunoglobulin molecules.
NH 3 +
component of the δ chain. A distinct exon encodes the
carboxyl terminal portion of the human δ chain that is
secreted. The human δ chain contains three N-linked oligosaccharides.
Two δ chains and two light chains, either κ
or λ, fastened together by disulfide bonds constitute an IgD
molecule.
immunoglobulin domain
An immunoglobulin heavy or light polypeptide chain structural
unit composed of approximately 110 amino acid residues.
Immunoglobulin functions may be linked to certain
domains. There is much primary and three-dimensional
structural homology among immunoglobulin domains.
A particular exon may encode an immunoglobulin domain.
In addition to immunoglobulins, these three-dimensional
globular structural motifs may also be identified in T cell
receptors and major histocompatibility complex (MHC)
molecules. The amino acid residues are folded into a
sandwich-like structure consisting of two β-pleated sheets,
each layer of which is comprised of three to five strands of
anti-parallel polypeptide chains fastened together by a disulfide
bond. Immunoglobulin domains may be designated
as V-like or C-like based on their homology to immunoglobulin
V or C domains.
immunoglobulin E (IgE)
IgE constitutes less than 1% of the total immunoglobulins
and has a half-life of approximately 2.5 days. This antibody
has a four-chain unit structure with two ε heavy chains
(molecular weight 75,000 Da each) and either two κ or two
λ light chains per molecule (total molecular weight 190
kDa). IgE does not precipitate with antigen in vitro and is
heat labile. IgE is responsible for anaphylactic hypersensitivity
in humans. It is elevated and plays a beneficial role in
parasitic infections.
immunoglobulin chain
A 72-kDa, 550-amino acid residue, heavy polypeptide
chain comprised of one variable region designated V H and a
I