B lymphocytes Flashcards
How many days does it take for the adaptive immune response to develop + become effective?
4-7 days
What are 2 forms forms of the adaptive immune response?
- Humoral: B cells, antibodies
- Cell-mediated: T cells, cytokines, lysis of pathogens
Where do B cells mature?
one marrow, whereby they express specific B cell receptors (BCR)
Where does antibody production following B cell activation and differentiation occur?
peripheral lymphoid organs
What are the 4 stages of B cell maturation?
Pro-B Cell -> Pre-B Cell -> Immature B Cell -> Mature B Cell
What is the B ell receptor?
transmembrane protein complex composed of: mIg + Igα/Igβ
What is the function of mIg that forms the B cell receptor?
central larger immunoglobulin molecule, cytoplasmic tail too short so not involved in signalling
What is the function of mIg that forms the B cell receptor?
central larger immunoglobulin molecule, cytoplasmic tail too short so not involved in signalling
What are Igα/Igβ that form the B cell receptor?
dil-sulfate linked heterodimers, contain immunoglobulin-fold structure. cytoplasmic tails of Igα/Igβ long enough to interact with intracellular signalling molecules
Which structures forming the B cell receptor interact with intracellular signalling molecules?
Igα/Igβ - cytoplasmic tails. mIg cytoplasmic tail too short
Which structures forming the B cell receptor interact with intracellular signalling molecules?
Igα/Igβ - cytoplasmic tails. mIg cytoplasmic tail too short
What does the unique binding site of B cell receptors bind to?
antigenic determinent/ epitope
How are BCR coded for on chromosomes?
kappa and lambda light chains and the ehavy chain are encoded by separate multigene families on different chromosomes - during maturation, segments are rearranged and brought together to form BCR (immunoglobulin gene rearrangement)
What are 4 types of segments within genes responsible for encoding the BCR chain?
- variable, V
- diversity, D
- joining, J
- constant, C
Which chain of the BCR is the diversity gene segment responsible for?
heavy chain only
In summary what generates the diversity of the B cell lymphocyte repertoire?
immunoglobulin gene rearrangement - occurs during maturation of B cells in the bone marrow
What type of DNA is involved in the synthesis of prototypical B cell membrane proteins?
Genomic DNA -> transcription -> primary transcript RNA/pre-mRNA -> Splicing -> Mature mRNA -> trnalsation -> membrane protein
What is the process resulting in light chain synthesis?
Germline DNA -> rearrangement of V and J segments involving VDJ recombinase -> B cell DNA -> transcription -> primary trancript RNA/pre mRNA -> splicing -> mature RNA -> translation -> light chain polypeptide (kappa or lambda)
Which enzyme is important in rearrangement of V+J segments of germline DNA important for heavy and light chain synthesis?
VDJ recombinase
What happens to unused DNA during joining of gene segments for light chain synthesis?
looped out and removed
What is the process of heavy chain synthesis from gene encoding?
Germline DNA –> rearrangement of V and J segments involving VDJ RECOMBINASE –> B cell DNA –> Transcription –> Primary transcript RNA/pre-mRNA– (Alternative Splicing) –> Mature mRNA –> (translation) –> Heavy chain polypeptide
Which DNA are B cell receptor membrane proteins derived from?
genomic DNA
Which DNA are B cell receptor heavy and light chain proteins derived from?
germline DNA
Which DNA are B cell receptor heavy and light chain proteins derived from?
germline DNA
