Innate Immunity Flashcards
List 3 physical barriers of innate immunity.
1 - Skin.
2 - Lungs.
3 - Gut mucosa.
List 3 factors that affect the commensal bacteria of the body.
1 - Illness.
2 - Diet.
3 - Age.
What is the immune function of paneth cells?
To secrete antimicrobial peptides such as defensins.
Where are paneth cells found?
Deep to the layer of mucosal cells.
List 4 properties of the innate immune response.
1 - Ready to rapidly activate at any time.
2 - No memory.
3 - Low specificity.
4 - Generic response.
Define erythema.
Redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries.
List 3 possible causes of erythema.
1 - Injury.
2 - Infection.
3 - Inflammation.
List 4 acute phase responses of the innate immune response.
For each, give an example of a consequence of the response.
1 - Vasodilation (erythema).
2 - Increased vascular permeability (oedema).
3 - Cytokine release (heat and inflammation).
4 - Nerve stimulation (pain).
List the 3 types of cells that form the innate immune system.
1 - Professional antigen presenting cells (APCs).
2 - Phagocytes.
3 - Granulocytes.
List 2 professional antigen presenting cells (APCs).
Monocytes:
1 - Macrophages.
2 - Dendritic cells.
List 2 phagocytes.
1 - Macrophages.
2 - Neutrophils.
List 4 granulocytes.
1 - Neutrophils.
2 - Eosinophils.
3 - Basophils.
4 - Mast cells.
What is the origin of macrophages?
Macrophages originate from monocytes which leave the circulation to differentiate in tissues.
List 4 examples of macrophages.
For each, describe their function.
1 - Alveolar macrophages phagocytose pathogens of the lungs.
2 - Kupffer cells in the liver assist in liver remodelling and defend against bloodborne pathogens.
3 - Microglial cells in the CNS eliminate old and dead neurones.
4 - Splenic macrophages in the red pulp of the spleen eliminate old red cells and bloodborne pathogens.
What is the primary function of dendritic cells?
How do they carry out their function?
- They are specialised to present antigens.
- They convert captured antigenic proteins into peptides.
- They then transport these peptides to their cell surface and present them on major histocompatibility complex (MHC molecules).
- This stimulates T cells to activate the adaptive immune response.
List 3 components of the granules of granulocytes.
1 - Inflammatory proteins.
2 - Toxic enzymes.
3 - Oxygen radicals.
List the granulocytes that are important for the acute and allergic phase response of the innate immune response.
1 - Mast cells.
2 - Basophils.
What is the primary function of eosinophils?
To kill parasites.
What are pattern recognition receptors (PRRs)?
Where are they found?
- They are receptors that bind to and recognise pattern-associated molecular patterns (PAMPs) that are present on microbes.
- They are found on and in every innate immune cell.
List the four families of pattern recognition receptors (PRRs).
For each, state whether they are intracellular or extracellular.
1 - Toll-like receptors (TLRs, extracellular but may also be present on endosomes).
2 - C-type lectin receptors (CLRs, extracellular).
3 - NOD-like receptors (NLRs, intracellular).
4 - RIG-1 like receptors (RLR, intracellular).
List 6 bacterial molecules (PAMPs) that might bind to pattern recognition receptors (PRRs).
1 - Lipoteichoic acid (LTA).
2 - Peptidoglycan (PGN).
3 - Lipoproteins.
4 - DNA.
5 - Flagellin.
6 - Lipopolyssacharide (LPS).
Give an example of a parasitic molecule (PAMP) that might bind to pattern recognition receptors (PRRs).
GPI anchors.
Give an example of a fungal molecule (PAMP) that might bind to pattern recognition receptors (PRRs).
Which fungal organisms express this molecule?
Where is this molecule expressed on these organisms?
- Zymosan.
- It is found on the cell wall of yeast.
What does pattern recognition receptor binding cause?
An intracellular cascade that stimulates the production of cytokines.
What is IRAK4 involved in?
What are the symptoms of an IRAK4 deficiency?
- IRAK4 is involved in the toll-like receptor pathway.
- IRAK4 deficiency results in recurrent streptococcal and staphylococcal infection as a child.
- People with an IRAK4 deficiency also get no fevers as there is no upregulation of inflammatory cytokines.
Why do the symptoms of an IRAK4 deficiency improve with age?
Due to an improved adaptive immune response.
List 3 proteins that are important in the innate immune response.
1 - Cytokines.
2 - Acute phase proteins (e.g. C reactive protein).
3 - Complement (a cascade of proteins).
What is the function of acute phase proteins?
To opsonise and present pathogens to the immune system.
List 5 functions of the complement cascade.
1 - Opsonisation.
2 - Killing of pathogens.
3 - Activation of immune cells.
4 - Chemoattraction.
5 - Inflammation.
List 4 functions of cytokines.
1 - Pro-inflammatory functions.
2 - Anti-inflammatory functions.
3 - To influence cellular differentiation.
4 - To direct cellular migration.
List 6 families of cytokines.
1 - Interferons.
2 - Chemokines.
3 - Tumour necrosis factor family.
4 - Interleukins.
5 - Haematopoietins.
6 - Transforming growth factor beta family.
What is the function of interferons?
They are antiviral proteins.
List 3 functions of chemokines.
1 - To direct cell migration.
2 - Adhesion of leukocytes to the endothelium.
3 - Activation of immune cells.
What is the function of the tumour necrosis family?
Regulation of inflammatory and immune responses.
What is the function of haematopoietins?
Promote cell proliferation and differentiation.
What is the function of the transforming growth factor beta family?
Regulation of immune cells.
Define opsonisation.
The process by which a pathogen is coated with proteins that facilitate phagocytosis.
List 3 ways by which opsonisation can occur.
1 - By the complement cascade.
2 - By C reactive protein and other acute phase proteins.
3 - By immunoglobulins (antibodies).
Which cells produce immunoglobulins?
B cells.
List 2 receptors that may be found on the surface of phagocytes that bind to opsonins.
For each, give the molecule to which they bind.
1 - CR1 receptor (binds to complement proteins).
2 - Fc receptor (binds to various immunoglobulins / antibodies).
List the 3 mechanisms of complement activation.
1 - Classical pathway.
2 - Lectin pathway.
3 - Alternative pathway.
What initiates the classical pathway of complement activation?
Antibody / antigen binding.
What initiates the lectin pathway of complement activation?
Carbohydrate sugars such as mannan.
What initiates the alternative pathway of complement activation?
Direct contact with microbial polysaccharides.
What is the first step in the complement cascade for all pathways?
Where in the body are the molecules that are involved in the initial steps of the cascade found?
- Cleaving inactive protein C3 to C3b and C3a.
- Inactive C3 is found circulating in the serum until the cascade is triggered.
How do the classical pathway, lectin pathway and alternative pathway start the complement cascade?
- The classical and lectin pathway use protein C4b2a to cleave protein C3.
- The alternative pathway uses protein C3bBb to cleave protein C3.
- Both C4b2a and C3bBb are types of C3 convertase.
What is the function of C3a?
C3a is an anaphylatoxin (triggers degranulation).
What is the function of C3b (outside of the complement cascade)?
C3b is an opsonin.
What is the fate of C3b if not used as an opsonin?
1 - Used for C5 activation.
2 - Can be converted back to C3bBb in a process known as the C3b amplification loop.
How does complement activation lead to inflammation?
C3a triggers the release of histamine from mast cells.
How does complement activation lead to cytolysis?
The complement cascade forms a membrane attack complex (MAC) which punches holes in microbial membranes.
Describe the process of C5 activation.
C3b and C5 convertase cleave C5, producing C5a and C5b.
Which component of the complement cascade causes chemoattraction?
Which cell is targeted by this chemoattraction?
- C5a.
- Attracts neutrophils.
List 2 regulatory proteins of the complement cascade.
1 - C1 esterase.
2 - Complement control protein.
