ToB - Immunity Flashcards
How do epithelia respond to pathogen attack?
1) . They are activated upon attack.
2) . Produce cytokines (cause some cells behaviour to alter) then chemokines (attract other cells and allow leakiness) = fluid migration occurs.
3) . Opsonisation occurs (complement in blood stream)
4) . Phagocytosis
5) . Interaction of macrophage etc. with T helper cells.
What is the function of the epithelia in immunity?
Form the first barrier of the innate immune system to pathogens.
What can epithelia produce in terms of immune response?
1) . Cytokines - proteins that act as chemical messengers to alter the behaviour of a cell.
2) . Chemokines - proteins that attract other cells and cause them to leak.
3) . Natural antibiotics - cathelicidens, defensins
4) . MAY PRODUCE - mucins, acid
What do inflammatory mediators do and what does this result in?
They promote vascular permeability
= leakage of antibodies and complement
= movement of macrophages, neutrophils and lymphocytes into tissues from blood stream.
What are the phagocytosis performing cell components of the innate immune system and what do they do?
Neutrophil
- specialised for anaerobic conditions (as this prevails in damaged tissue)
- aided by receptors for bacterial constituent so can bind to bacterium and as a result phagocytose better
- contain granules of NADPH oxidase (oxidative burst) and lysozymes (phagocytosis) but once these run out, more cannot be synthesised
Monocyte/macrophage
- also act as antigen presenting cells
- aided by opsonisation
- release cytokines that activate the T lymphocytes
What are the cellular components of the innate immune system that perform allergic reactions, and what is their function?
Eosinophils - antiparasite
Basophils - protect mucosal surfaces
Mast cells - protect mucosal surfaces
What part of the immune system are natural killer cells part of, how are they activated and what is their function?
Part of the innate immune system.
Activated by cytokines released by macrophages (IL-12) and a chemical (IFNalpha/beta) released upon viral infection.
Induce apoptosis in a virus infected or cancerous cell.
What is opsonisation?
The bacteria is coated with complement or antibodies.
Complement receptors are on phagocytes = mediate engulfment after binding.
Granules can now fuse and kill the pathogen.
What are the humoral components of the innate immune system and their function?
Transferrin/lactoferrin - deprive bacteria of iron
Interferon - activate NKCs, inhibit viral replication
Lysozyme - breaks down cell wall of some gram positive bacteria
Fibronectin - opsonisation
Complement - kill microbe, aid in phagocytosis
TNF-alpha - inhibit viral replication, activates phagocytosis
What does complement 3B do?
Binds to bacteria covalently and opsonises it.
How can complement components kill a bacterium?
1) . C5-9 form a complex which binds to the bacteria membrane.
2) . C8 binds and inserts into membrane
3) . C9 binds to complex and causes polymerisation (forms the loop) = pore forms
= lysis of cell.
What is the flow chart of adaptive immunity?
Common lymphoid precursor
= T cell = B cell
= CD4+ (helper) CD8+ (cytotoxic) = plasma cell
What is the difference in antigen receptors of B cells and T cells?
In T cells, they are non membrane bound molecules (get released) = T cell antigen receptor
In B cells, they are membrane bound
= surface immunoglobulin
What are the cellular components of the adaptive immune system and their functions?
B cell
- activated by CD4+ cells
- release cytokines
- divide to give plasma and memory cells
T cytotoxic cell (CD8+)
- release perforin when cell is infected (destroys cell walls)
T helper cell (CD4+)
- activated when CD4+ binds to an antigen on an antigen presenting cell
- clones to form helper cells
- activates B cells
What do plasma cells provide?
Antibodies
What are the humoral components of adaptive immunity?
1) . Cytokines (e.g. CD4+ activates B cells)
2) . Perforin - released by T cytotoxic cells to destroy cell walls
3) . Antibodies
How do antibodies help with immunity?
1) . Neutralisation - bind to bacteria, preventing them from adhering to healthy cells
2) . Opsonisation - bind to bacteria and then are detected by receptors on macrophages = aids phagocytosis
3) . Complement activation - aids opsonisation.
What is clonal selection in immunity?
Each lymphocyte has only one specific antigen = needs cloning before mounting an effective response.
This takes 3-5 days after the lymphocyte bearing the complimentary receptor to the foreign antigen is detected.
What is the basic sequence of events in an adaptive immune response?
1) . Clonal selection
2) . Clonal expansion
3) . Differentiation to effector cells
4) . Antigen elimination
5) . T and B cell apoptosis
Compare and contrast the innate and adaptive immune system.
Innate born with, adaptive is acquired.
Innate doesn’t have a memory, adaptive does.
Innate is non specific, adaptive has specific lymphocytes used
Innate is not enhanced by a second exposure, adaptive reacts much quicker due to presence of memory cells.
How can complement be destroyed or deficient?
By heat
By genetic defect causing a deficiency in a specific complement.
