Lymphocytes : Cells with
receptors that are highly
specific
Cell mediated Tcells
originate in bone
marrow but mature
in thymus and
found tissue and
blood
Naieve Tcell
CD4+
CD8
Humoral Bcells
cells origniate and develop
in the bone marrow
Naieve Bcell
Nota:
Activated when the antibody on the B cell recognises an antigen through contact with epitome engulfs it and presents it throgugh an MHC CLASS 2 - helper T cell then comes along rtecognises it and assist B cells to differenciate
Plasma Cells
Antibodies
Structure
Nota:
Composed to two heavy chains , two domains and two chains.
Has a variable domain and constant domain
Light chain and heavy chain '
Fc regioin binds to other cell
Fab regions binds to antigen
Function
Neutralisation
Nota:
Neutralization
o Bind to the surface of pathogen
o Prevents adherence or infection of host cells
Oponisation
Nota:
1q binds to a platform created by hexameric IgG
This produces inflammatory mediators, which produce opsonins
Production of opsonins
o Opsonins bind to antigen
o Enhanced clearance by phagocytes that recognise the Fc portion of the antibody
o Opsonisation is the alteration of the surface of the pathogen/particle that increases the rate
at which it is phagocytosed
Deposition of pore forming protein
Lysis
Nota:
Complement mediated lysis of cells that are coated by
antibody (particularly IgM and IgG)
Complement is a series of serum proteins that interact with each other in a cascade. Important role
in responses to bacteria and viruses.
Antibody dependent cellular toxicity
Nota:
Antibody dependent cellular cytotoxicity
Cells such as NK cells can kill cells that are coated by antibody NK cells will not kill free antigen
Limited to viral infection – Cant kill antibody coated bacteria
diversity
Nota:
The diversity comes from the splicing that occurs with the genes.
Heavy chain is encoded by VDJC and
Light chain is encoded by VJC
recombination creates unique antibodies per cell
Rearrangment VH3DH7JH5 = all matieral b/w v3 to d7 is deleted along with matieral b/w d7 to h5 all the matieral upstream and downstream kept
Types
Nota:
Variation in heavy chain constant regioin detemines isotype
Intially make IgM in naieve cells but then upon maturation make isotypes throgyuh class swithching as the variable regions remainsthe same the specifiicity does not chain just the affinity
IGM
Nota:
-expressed in naeive B cells
-pentamer
-not a high affinity antibody
-linked by J chains
-very effiecient activating compliment
IGG
Nota:
Major class is serum
major class in secodnary response
binds receptor exposed by monocytes
IGA
Nota:
Forms a monomer when its on the cell surface (bivalent) and dimer (tetravalent) when its secreted
Dimer is held together by a J chain that binds to the secretory component
The secretory IgA is prominent in mucosal secretions – airways, gut, breast milk
Best for vaccines
IGD
IGD
Nota:
gD
On naïve b-cells
Found in low amounts in serum
Monomer
Similar to IgG but cannot cross placenta and does not activate complement
No effecter complement – cleaved off cell surface. Just recepto
IGE
Nota:
Found in trace amounts in serum
Monomer
Important in responses to parasites
Can cause allergic reactions
Memory Cells
A body's ability to resist a particular
diesase whether natural or as a result
of a previous infection
Antigen : molecules recognnised by
immune system inducing an immune
response. Can be prtoeins ,
carbohydrates , nucleic scid , lipids or
lipopolysacharides