Untitled - D Ank Unlimited

class II region 176 class switching (isotype switching)
W X1 X2 Y
Regulatory sequences
by other types of cells. Antigen-presenting cells (APCs)
such as macrophages present antigen at the cell surface
to immunoreactive CD4 + helper/inducer T cells in the
context of MHC class II antigens. For appropriate presentation,
the peptide must bind securely to the MHC class II
molecules. Those that do not bind fail to elicit an immune
response. Following interaction of the peptide and the CD4 +
helper T lymphocyte receptor, the CD4 cell is activated,
interleukin-2 (IL2) is released, and the immune response
is initiated. In humans, the class II antigens DR, DP, and
DQ are encoded by HLA-D-region genes. In mice, class II
antigens, designated as Ia antigens, are encoded by I-region
genes. The I invariant chain (Ii) represents an essentially
nonpolymorphic polypeptide chain associated with MHC
class II molecules of humans and mice.
class II region
That part of the major histocompatibility complex (MHC)
containing the MHC class II α and β chain genes.
class II transactivator (CIITA)
Refer to MHC class II transactivator.
α5'
NN s
s
α1 β1
α2
Papain cleavage site
C
s
s
Papain cleavage site
C
Leader
sequence
TATA
Class II MHC molecules are glycoprotein histocompatibility antigens
that play a critical role in immune system cellular interactions. Each class
II MHC molecule is comprised of a 32- to 34-kDa α chain and a 29- to
32-kDa β chain, each of which possesses N-like oligosaccharide groups,
amino termini that are extracellular, and carboxyl termini that are intracellular.
Approximately 70% of both α and β chains are extracellular.
s
s
β2
Class II MHC.
α1
N
Transmembrane
and cytoplasmic
α2
β 1
3' Untranslated
sequence
β 2
class II vesicle (CIIV)
A murine B cell membrane-bound organelle that is critical
in the major histocompatibility complex (MHC) class II
pathway of antigen presentation. It contains all constituents
requisite for the formation of peptide antigen and MHC
class II molecular complexes, including the enzymes that
degrade protein antigens, class II molecules, invariant
chain, and HLA-DM.
class III molecules
Substances that include factors B, C2, and C4 that are
encoded by genes in the major histocompatibility complex
(MHC) region. Although adjacent to class I and class II
molecules that are important in histocompatibility, C3
genes are not important in this regard. The 100-kB region is
located between HLA-B and HLA-D loci on the short arm
of chromosome 6 in humans and between the I and H-2D
regions on chromosome 17 in mice. The genes encoding C4
and P-450 21-hydroxylase are closely linked.
class III region
That area of the major histocompatibility complex between
the class I and class II regions, called the central MHC. No
MHC class I or class II genes are present in this region.
class switching (isotype switching)
A change in the isotype or class of an immunoglobulin
synthesized by a B lymphocyte undergoing differentiation.
3'
Peptide-binding
cleft
MHC class II molecular structure.
C
α 1
α 2