B Cell maturation, differentiation and activation
B CELL
B-cell Receptors
The binding specificity of an antigen depends on the receptors of b
cells. The B cells receptors are present on the B cell surface and are
present both above and below the plasma membrane of the cell. The
receptor of B cell has two parts, a signal transduction portion and
membrane bound Ig molecule which is the antigen binding subunit.
The membrane immunoglobulin molecule consists two of each heavy
and light chains. The heavy chain can be an immunoglobulin isotope
G, A, M, D or E while the light chain is either lambda or kappa. There
are further two regions in both heavy and light chains; variable and
constant region. The variable region is responsible for antigen binding
while the constant region is responsible for biological activity. The
identical heavy and light chains are held together by the disulphide
bonds.
Maturation
The maturation of B cells starts from the rearrangement of the gene
segments in the heavy and light chain. First the V, D and J segments
rearrange in the heavy chain during the pro B cell stage. When the
rearrangement completes in the heavy chain, the cell is called as pre B
cell after which the rearrangement of the V-J segment occurs in the
light chain producing a complete B cell receptor on immature B cells
with the specificity of IgM on the cell surface. The immature B cells
now move the spleen where they go through transitional stages called
T1and T2. After differentiation the B cell reaches maturity.
B CELL
B-cell Receptors
The binding specificity of an antigen depends on the receptors of b
cells. The B cells receptors are present on the B cell surface and are
present both above and below the plasma membrane of the cell. The
receptor of B cell has two parts, a signal transduction portion and
membrane bound Ig molecule which is the antigen binding subunit.
The membrane immunoglobulin molecule consists two of each heavy
and light chains. The heavy chain can be an immunoglobulin isotope
G, A, M, D or E while the light chain is either lambda or kappa. There
are further two regions in both heavy and light chains; variable and
constant region. The variable region is responsible for antigen binding
while the constant region is responsible for biological activity. The
identical heavy and light chains are held together by the disulphide
bonds.
Maturation
The maturation of B cells starts from the rearrangement of the gene
segments in the heavy and light chain. First the V, D and J segments
rearrange in the heavy chain during the pro B cell stage. When the
rearrangement completes in the heavy chain, the cell is called as pre B
cell after which the rearrangement of the V-J segment occurs in the
light chain producing a complete B cell receptor on immature B cells
with the specificity of IgM on the cell surface. The immature B cells
now move the spleen where they go through transitional stages called
T1and T2. After differentiation the B cell reaches maturity.
