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Lambda light
chains
4 C region genes, (one for each subtype of lamdachain) 30 V region genes. Each of the V region genes iscomposed of two exons, one (L) that codes for a leader region the other (V) that codes for most of the variable region. Upstream of each of the C genes there is andadditional exon called J (joining). The L, V, J and C exons are separated by introns(intervening non-coding sequences). TERM 2
Kappa light
chains
DEFINITION 2 Only one C region gene, since there is only one type of kappa light chain. There are many V region genes a leader exon and a V exon. Several J exons located between the V and C genes. All of the exons are separated by introns TERM 3
Ig heavy chain
DEFINITION 3 Many C genes, one for each class and subclass of immunoglobulin. Each of the C genes is actually composed of several exons, one for each domain another for the hinge region Many V region genes, each composed of a Leader V exon Several J exons Additional exons called the D (diversity) exons. TERM 4
2 rearrangements at DNA
level
DEFINITION 4 1- one D region is brought next to the J region 2- one V gene is brought next to the DJ region The recombination events removes the introns between V, D and J regions TERM 5
The pre-mRNA can be processed in two ways,
DEFINITION 5 bring the VDJ next to the Cmu gene to bring the VDJ next to the Cdelta gene. The resulting mRNAs have the L, V, D, J and Cmu or Cdelta exons contiguous and will code for a mu and a delta chain, respectively.
mechanism of DNA
rearrangements
recombination signal sequaneces (RSS) -nonmer -Heptamer - 1 or 2 turn signalsRag-1 and Rag- TERM 7
Ig order of gene expression
DEFINITION 7 An individual B cell only produces one type of light chain and one class of heavy chain. Since any B cell has both maternal and paternal chromosomes which code for the immunoglobulin genes there must be some orderly way in which a cell expresses its immunoglobulin genes so as to ensure that only one type of light chain and one class of heavy chain is produced. TERM 8
The orderly sequence of rearrangements in
the immunoglobulin gene families explains:
DEFINITION 8 Why an individual B cell can only produce one kind of immunoglobulin with one kind of heavy and one kind of light chain. Why a individual B cell can only make antibodies of one specificity. Why there is allelic exclusion in immunoglobulin allotypes at the level of an individual immunoglobulin molecule but co-dominant expression of allotypes in the organism as a whole. TERM 9
Heavy Chain Order
DEFINITION 9 A cell first attempts to rearrange one of its heavy chain genes: maternal chromosome or paternal chromosome is selected. If the rearrangement is successful so that a heavy chain is made, then no further rearrangements occur in the heavy chain genes. If, on the other hand, the first attempt to rearrange the heavy chain genes is unsuccessful (i.e. no heavy chain is made), then the cell attempts to rearrange the heavy chain genes on its other chromosome. If the cell is unsuccessful in rearranging the heavy chain genes the second time, it is destined to be eliminated. TERM 10
Light Chain Order
DEFINITION 10 If cell successfully rearranges a heavy chain: Attempts to rearrange one of its kappa light chain (maternal or paternal), if fails tries the other chromosome. If successful it will be a B cell that expresses a kappa light chain. If a cell fails to rearrange a kappa light chain it will attempt to rearrange a lambda light chain (m or p) etc.
IgD constant region
structure monomer tail piece TERM 17
IgE constant region
DEFINITION 17 structure monomer extra domain (CH4) TERM 18
Mature naive B cells express
DEFINITION 18 both IgM and IgD at their surface. TERM 19
class switching
DEFINITION 19 Immunoglobulin class switching) is a biological mechanism that changes a B cell's production of antibody from one class to another, for example, from an isotype called IgM to an isotype called IgG. TERM 20
somatic hypermutation
DEFINITION 20 DNA point mutation that is irreversible in B-cells.not in T-cells
