Immunology 2 Flashcards
What proviides the first line of defence?
Epithelial Surfaces e.g. skin, gut, bronchi
In the skin epidermis, what do keratinocytes do in the stratum spinosum?
Produce a waterproof antimicrobial layer
In respiratory epithelium, what do goblet cells secrete and what does it do? (2 marks)
- Secrete mucins
- Mucus layer traps foreign particles which are cleared by the muco-ciliary escalator - allows for FLOW
In the gut epithelium, how does peristalsis work to reduce bacterial infection and what do paneth cells do? And urinary tract?
(3 marks)
- Peristalsis will move food and infectious agents creating a nice FLOW
- Paneth cells produce several types of antimicrobial proteins
- Urinary tract also maintains the FLOW and prevents kidney infections
What are the humoral components of the innate immune system?
- Complement system
- Defensive chemicals
- Peptides
- Enzymes
Where are microbicidal and microbiostatic chemicals found? GIve examples of these. (3 marks)
-
Digestive tract:
- stomach acid
- digestive enzymes
- bile salts
Acidic and create a bad environment for bacteria
Where can antibacterial enzymes that are secreted be found? Give an example of these. (3 marks)
- Found in tears, saliva and paneth cells:
- Lysozyme (breaks down cell wall)
- Secretory phospholipase A2 (breaks down plasma membrane)
What are antimicrobial peptides (AMP) and where can they be found? (3 marks)
- Secreted by epithelial cells into mucosal fluid to produce antimicrobial peptides
- Secreted by phagocytes into tissues
- E.g. defensins, cathelicidins, histatins
What are defensins and how do they work? (4 marks)
- Short peptide with hydrophobic and hydrophilic regions - this allows them to disrupt the membrane very quickly
- Attracted first to phospholipids on bilayer
- Slips through bilayer and creates a pore which allows fluid to come out of bacteria
- Loss of fluid in bacteria means can no longer maintain its pH
- Thus causing death of bacteria
What are cathelicidins and what do they do? (4 marks)
- amphipathic peptide with hydrophobic and hydrophilic region
- Bind to plasma membrane and wrap it up into little balls
- Break down bilayer by dissolving into little balls
Where are catheliciins:
A. Constitutively expressed
B. Induced expression
(2 marks)
A. Myeloid progenitor cells
B. Induced during bacterial infection
Explain the process of the function of the complement system (6 marks)
- Small proteins circulate in plasma found in interstitial fluid - whilst here are inactive. Proteins able to leave with plasma
- Bind directly to surface of pathogen or complement protein can bind to carbohydrate sequences and initiate activation of other complement proteins
- Once bound = protelytically active. Can split themselves in 2 (A,B). Some parts biologically active to kill pathogen and others can cleave themselves in 2.
- B part combined with another b can turn into another proteolytically active enzyme which can cleave another protein into 2 Ca and a Cb.
- Ca will go off to kill and Cb will re-join with another b so you will get a cascade of proteins that create either Ca and b and so forth
This is known as amplification of production of portions of complements
What is the role of C3 and C5 in the complement system? (6 marks)
C3:
- can bind directly to surface of pathogen and then enzymatically split itself in 2 to 3b and 3a
- 3a has role in inflammation, 3b activates opsonisation (assisting phagocytosis) also has role in converting c5 to c5a and c5b
- 3b binds with another 3b to split c5
C5:
- 5a involved in inflammation
- 5b involved in creating membrane attack complex - which is a type of pore that kills pathogen inside of it by leaking fluid out of pore
Binding of 2 complement proteins to surface of pathogen will also induce enzymatic splitting of c3 into b which will create a cascade to create other c protein parts
How does vascular permeability occur in an infected capillary? (3 marks)
- C3a and 5a bind to part of endothelial cells and tells them to pull a part to allow more plasma to come out = VASCULAR PERMEABILITY
- This increases fluid in tissue and induces expression adhesion molecules inside of capillary
- More plasma in tissue = more complement proteins
What is the effect of pore formation from terminal complement proteins C5b and C6-9?
- Pore is formed in lipid bilayer of membrane which destroys proton gradient as - unstable pH, so no drive to proton pump, no voltage and no energy
- Pore destroys membrane integrity and fluid in bacteria floods out causing pore destruction