Lymphocyte Development in Bone Marrow and Class Switching Flashcards
what myeloid cells
monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, dendritic cells, and megakaryocytes or platelets
what are lymphoid cells
T cells, B cells, and natural killer cells
what happens to preB cells
undergo Ig gene rearrangement to produce one specific Ig. preB cell-> naive Bcell, expressing cell surface IgM.
go tp secondary lymph organs
what happens to preT cells
go to thymus and mature there
what are the two broad phases of humoral immunity
recognition phase and activation phase
what happens in the activation phase of humoral immunity
bcell clonal expansion differentitaion (Ig secretion, memory cell, affinity maturation, class switching)
what happens to naive bcells
sit in lymphoid organs. On exposure to its specific antigen, become activated.
needs stimulation from CD4+ and cytokines
how is activation of bcells regulated
needs stimulation from CD4+ and cytokines
what happens to the cells of clonal expansion of bcells
become:
- memory bcells
- plasma ells (Ig secretion)
- affinity maturation
- class switching
what happens to the first Ig produced by the Ig produced bt the naive bcell
is expressed as a membrane Ig. acts a receptor to recognise the Ig.
Stimulates signalling pathways to activate the bcell
what are the two forms of Ig
membrane bound
secreted into mucosa, circulation, tissue
how does the bcell switch being membrane Ig to having plasma secrete Ig
differential splicing of the exons of C segment of RNA
what part of the RNA encodes the Fc region
is not coded for by a single exon, but 4 exons that need to be transcribed and then spliced to make mature mRNA
RNA polymerase transcribes whole primary transcript. What happens if it is needed to be secreted
translated protein will contain amino acids that make it secreted
RNA polymerase transcribes whole primary transcript. What happens if it is needed to be in membrane
RNA polymerase transcribes whole primary transcript. What happens if it is needed to be secreted
three ways in which secreted Ig deal with pathogens
neutralisation
opsonisation
activation of complement
what is opsonisation
pathogen coated by antibodies.’. flagged.
Fab region binds to antigen, Fc region bind to Fc receptor on a phagocyte, facilitating phagocytosis
Role of Ig in neutralisation
antibodies bind to pathogens, this means that the viral particles are prevented from attaching to host cells. Thus viral genome cannot be taken up
reason for class switching
B cell antibodies to perform different effector functions and deal better with pathogens
DOES not alter specificity
what bit changes when Ig undergoes class switching
Constant heavy chain
CH region
what class of Ig is produced first
IgM
How is IgD made
made at same time as IgM. Bcell rearranges DNA to bring VDJ segments together.
whole gene is transcribed into primary transcript. RNA splices the unwanted J segments and constant region for mew OR delta heavy chain.
how is IgG,IgA,IgM,IgE made
different constant region = different class of antibody. (alternative constant segments) endonuclease have reconition sites before each heavy chain constant. Will cut a C segment (and Constant heavy chain) bring that S segment up so its next to VDJ original VDJ can be transcribed along with new C region
SO same specific Ig but with different constant heavy chain/different class. No change in light chain
Role of CD4+ cell in setiching to IgE
The CD40 ligand on the T cell interacts with CD40 on B cells
The T cell then produces cytokines that tells the B cell what to do
If it secretes IL-4 -> B cell will switch to IgE
