Immune 7 Flashcards
What’s a good example of th innate system interacting with the adaptive system
Antibody stimulating activation of complement
Process he talks about at the start
- antigens being loaded into system and it being sampled by an APC (eg dendritic cell)
- dendritic cell stimulates several types of T cells (CD4 T cells - which then helps B cells make antibodies) by realising cytokines
- B cells make antibody and the antibody (on their cell surface) can then bind to antigens
- this activates them to become a plasma cell (anibody secreting cell)
(B cell requires two signals - bind to antigen and T cell help in the form of cytokines
B cell is regocising ‘native’ antigen (unprocessed antigen)
T cells recognise peptides (broken down antigens)
B cells regognise native, unprocessed antigens
B cells
- are lymphocytes that develop into the bone marrow
- express unique antigen receptors (BCR or secreted antibody)
- plasma cells are activated B cells that secrete antibody
- memory B cells provide ‘memory’
B cell surface when it is a naive cell (not producing secreted antibodies)
- antibody on surface of cell
- no secreted as to has a trnasmembrae domain
- a part of a group diverse B cells (different from one another
- structure of antibody: two identical light chains and two identical heavy chains
- bivalence
An antibody is composed of:
- two identical light chains
- two identical heave chains
B cell receptor (BCR)
- surface of each B cell is covered with ~100,00 BCR (mainly IgM / IgD antibodies)
- The BCR binds antigen and activated the B cell
- BCR is membrane ancohoured via a transmembrane dominion (TM). Secreted antibodies lack a TM.
Three functions of antibody
- Neutralisation (binding to a virus protein and blocking their interaction w host cells (talking))
- Opsonisation
- Complement activation
Viral neutralisation
- virus has receptors on surface that can bind to our host cell
- most viruses are host specific and will have a specific target to target something on our cell surface
- if antibody can be generated against virus protein, antibody will block it (block interaction of virus with host cells)
- toxin may also be able to attach to host tissue (host cells) and antibody can stop that from happening
Opsonisation
- opsonisation can occur by the antibodies binding to surface of the microbes
- makes bacterium more attractive e to phagocytes
Activation of complement system and pore formation
- antibody can activate complement (needs to be bound to surface)
- complement will form membrane atttack complex which forms a pore in the microbes surface
- this can lead to ion exchange or water influx
- some forms of antibody are better then others at activating complement
IgG antibody
- only produced by B cells and circulates for a long amount of time thus really abundant
Constant region (talking)
- antibody can differ by constant region
- constant region doesn’t contact the antigen
- constant region imparts a function upon the antibody
- isotypes only differ by the constant region
- doesn’t change the antigen that it targets
IgA antibody
- infant uptakes the IgA from the placenta and breast milk - passive immunity - got it from mum
Passive immunity
IgA in milk transferred to infant
- main mucosal antibody is able to be provided to baby’s through mums breast milk
- B cells when first developed in bone marrow theylll have lots of IgM on their cell surface as a monomer
- if its secreted by B cells it forms a pentameric form
- IgM present at the start of an immune response - very good at activating complement system
IgE
- binds to parasites and helps with their explosion from the body
- responsible for reactions to allergens
IgD
- not secreted
- B cell popping out of bone marrow has a mixture of IgM and IgD on cell surface
- acts as anigen receptor
Graph to remember
