Lymph Flashcards
T cells
2 Types:
memory and central memory
Activate > Proliferate > effector function > cell death by apoptosis (90%) leaving memory T cells
Memory T cells are long lived.
Immunological diversity
Antigen recognition
They are co-dominantly expressed, inherited from mother and father.
1) Surface immunoglobin or B cell receptor
secreted and transmembrane form
2) Antibody
transmembrane form only
3) T-cell receptor
B cells vs T cells
B cells occur as soluble and membrane bound
T cells only occur as membrane bound form
B cells recognise free antigen
stronger interaction with antigen than TCR
Transmembrane vs secreted
membrane bound form - heavy chain has hydrophobic transmembrane domain of -25 amino acid
T and B cell receptor
B cell and T cell express unique antigen receptor. FAB fragments
Encounter antigen > T cells divide > daughter cells share specificity from parental cells
They have common arching structure.
They have variable regions (V-regions) which contain hypervariable regions
V regions are found as fragments and assembled/re-arranged.
HEAVY CHAIN
The genes are located on chromosome 14!!
There are 3 different genes:
Variable, Diverse, Join
These 3 genes will combine with each other to form complexes.
Process:
D, J family re-arranges first
V, D, J re-arranges
(This occurs in the B-cells in the bone marrow)
Lastly, transcription
Upstream and downstream molecules are cut
The monitor is called the recombination signal sequences (RSS)
RNA processing
Translation
Transport to ER
k and l chain
They have only 2 families to recombine, found in chromosome 2, 22 respectively
B cells
undergoes primary diversification in the bone marrow.
they have IGM and IGD which leaves the cells
Can undergo secondary diversification
containes IGA and IGG
Primary: Gene segments, recombinant, junctional diversity (mistakes can happen), occurs in light and heavy chain.
Secondary : somatic hypermutation
Somatic Hypermutation (B cells)
Cells proliferate at high rate, high fidelity of mutation throughout re-arranged V region exon.
Mutant B cell receptors appear in the surface of B cells
Favourable mutation can occur, which increases affinity of BCR for antigen, preferentially selected to mature into antibody secreting cells.
B cell memory and plasma cells
They sit in the B-cell zones/Germinal centre
Naive cells enter the B cell zone, then proliferate, somatic hyperproliferation occurs
B cells encounters T helper cells, they interact by cytokines, T cells gives signal to B cells to change class of antibody.
Antibody - constant region
Downstream of the chromosome, constant region is found, contains different C fragments which determine the class of antibody
Immunoglobin class switching/ Isotype switching
comes down to the type the body needs.
T and B cells get signals from parasite.
T cells in lymph node get togther with the B cells.
T cells gives the signal to B cells of which class is needed to fight a specific parasite.
Isotype switching in ALLERGY
scenario: Allergen are taken into the body.
T cells respond to allergen, produce specific cytokines
Interleukin-4, is a signal to switch class (it is a cytokine)
B cell response
They are 2 types:
One is T cell dependant (CD4 T cells)
Other is independant which doesnt require help from T cells
T-dependant response:
T produce all kinds of cytokines
T-independant:
They do NOT undergo class switching, so they only make IGM
Antigen binds and cross-links membrane immunoglobin
Diversification of T cells
Only primary diversification
Each chain has 2 domains: variable and Join
Gene segments of families are selected and combined unique to a specific response
