Assignment 6 Flashcards
(54 cards)
what is the role of B lymphocytes?
express antigen recognizing receptors (antibodies) on their cell surface - the receptors mediate the interaction between the B cell and the intact antigen
- Interact with antigen and process/present it to CD4+ T cells
- Antibody factory following differentiation of plasma cells
- Some differentiation to memory B cells
- Express antigen receptors (mIg) on cell surface
- BCR complex
at what developmental phase does progenitor B cell acquire its antigen specific receptor (immunoglobulin)?
hematopoeisis
membrane immunoglobulin (mIg) are expressed in associated with heterodimer, ______
CD79a/CD79b = Ig alpha/Ig beta
what is the role of CD79a/CD79b = Ig alpha/Ig beta?
couples mIg to intracellular signaling pathways
in naive mature B cells, they heavy chain constant regions are ____ and ____, while the light chain constant regions are either _____ or _____
mu
delta
kappa
lambda
what segments make up the light chain variable region of the mIg?
V and J
variabel and joining
what segments make up the heavy chain variable region mIg?
V, D and J
variable, diversity and joining
the variable regions of the light and heavy chain are encoded in the genome by segments that are _______ during B cell development
randomly!
the constant regions, light and heavy chain differ from ______ but are the ____ in all antibodies
one another
same
why do light and heavy chains have more potential diversity for the B repertoire?
because they are not restricted in their association
where is the antigen binding site contain within?
combined variable regions of the light and heavy chain = hypervariable regions = complementary regions = paratope
what types of forces are between the antigen and antigen binding site on the antibody?
non-covalent - this means antigens can come on and off!
what does the attraction between the antigen binding site and an epitope determine?
affinity
the overall attraction, including all Fab regions is referred to as ?
avidity
the construction of different mIg on B cell clones is the result of?
- multiple copies of germline V,D and J gene segments
- random selection and combination of V,D, and J gene segments
- junctional diversity generated by the addition or deletion of bases
- random assortment of light and heavy chains
the random selection of V,D, and J gene segments generated B cell receptors that may be_____
autoreactive => those B cells must be deleted or inactivated!
define somatic recombination
the process in which DNA in the loci that encode the variable region is cut and recombined to make an intact gene for the variable regions of the light and heavy chains
the variable region gene and constant region genes are transcriibed into hnRNA which is spliced to mRNA which is translated to a light chain and a heavy chain
the variable region gene and constant region genes are transcriibed into hnRNA which is spliced to mRNA which is translated to a light chain and a heavy chain
where does transcription and translation of light and heavy chain genes occur?
bone marrow during B cell development
how many B cell clones can an individual generate? aka total diversity of BCR
10^9 to 10^11 - each having mIg whose variable regions will differ from those present on other clones
what do the B cell clones collectively represent?
B cell repertoire
how is the diversity among B cell clones possible?
because of V,D, and J segments which encode the variable regions and are present as multiple germline genes
how is recombination triggered?
activation of recombinases, nuelceoprotein products of the RAG-1 and RAG-2 genes (recombination activating genes)
gene rearrangement of the variable light chain involves the selection and ligation of what?
1 J and 1 V to = VJ segment
