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Claman, Henry 174 class I MHC molecules
Extracellular
matrix
Cytosol
Golgi
Protein
Claman, Henry
He conducted studies with lethally irradiated mice and
proved that both bursa-derived and thymus-derived lymphocytes
were needed to produce an immune response
(T and B cell cooperation).
C
An immunoglobulin λ light chain constant region. The corresponding
exon is designated Cλ. There is more than one
isotype in mice and humans.
class I antigen
A major histocompatibility complex (MHC) antigen found
on nucleated cells on multiple tissues. In humans, class I
antigens are encoded by genes at A, B, and C loci and in
mice by genes at D and K loci.
class I region
The segment of the major histocompatibility complex that
comprises the MHC class I heavy chain genes.
class IB genes
Genes linked to the major histocompatibility complex
(MHC) class I region that code for class I-like α chains.
These genes that encode molecules on cell surfaces that
associate with β 2 microglobulin vary in their cell surface
expression and tissue distribution from one species to
another. An individual animal may have multiple class IB
molecules. One such molecule has a role in presentation of
peptides bearing N-formylated amino termini. Other class
IB molecules may also be active in antigen presentation.
class I MHC molecules
Glycoproteins that play an important role in the interactions
of cells of the immune system. Major histocompatibility
complex (MHC) class I molecules occur on essentially all
nucleated cells of the body but are absent from trophoblast
cells and sperm. The cell membrane of T lymphocytes is
rich in class I molecules that are composed of two distinct
polypeptide chains: a 44-kDa α (heavy) chain and a 12-kDa β
chain (β 2 microglobulin). There is a 40-kDa core polypeptide
in the human α chain that has one N-linked oligosaccharide.
Approximately 75% of the α chain is extracellular, including
the amino terminus and the oligosaccharide group. The membrane
portion is an abbreviated hydrophobic segment. The
cytoplasm contains the 30-amino acid residue that comprises
the carboxyl terminus. The β 2 microglobulin component is
Class I
heterodimer
Class I TAP1
heterodimer
Proteasome
ER
lumen
TAP2
Peptides
Major histocompatibility complex (MHC) class I assembly.
α3
Calnexin
β 2m
Class I
H chain
α2 α1
s
s
s s
N
s
s
C
Papain cleavage site
linked to neither the cell surface nor the α chain by covalent
bonds. Its association with the α chain is noncovalent. Class I
molecules consist of four parts: an extracellular amino terminal
peptide-binding site, an immunoglobulin (Ig)-like region, a
transmembrane segment, and a cytoplasmic portion. The main
function of MHC molecules is to bind foreign peptides to form
a complex that T cells can recognize. The class I molecular
site that binds protein antigens is a 180-amino acid residue
segment at the amino terminus of the class I α chain. The α-3
segment of the heavy chain contains approximately 90 amino
acid residues between the carboxyl terminal end of the α-2
segment and the point of entrance into the plasma membrane.
The α-3 segment joins the plasma membrane through a short
connecting region and spans the membrane as a segment of
25 hydrophobic amino acid residues. This stabilizes the α
N
β 2 Microglobulin
Major histocompatibility complex (MHC) class I molecules are glycoproteins
that play an important role in interactions among cells of the immune
system.