Defenses and Deficiencies Flashcards
(33 cards)
What is the innate immune system?
A branch of the immune system that is always ready to react and eliminate pathogens. Does not need prior exposure to pathogen.
What are some key features of the innate immune system?
Causes inflammation, antiviral defense, stereotypical response, Recognizes ‘foreign vs self’
What are the physical barriers that pathogens encounter?
Tight junctions (endo/epithelial cells), Mucous (contain antiboitics), Cilia, Gut peristalsis, Other normal microbiota
What are the chemical barriers that pathogens encounter?
Acidic pH, Antimicrobial peptides, Lysozyme, Lactoferrin, Apolactoferrin, Surfactants and Antibodies.
Where is acidic pH in the body?
Skin, stomach, urine, vagina and bile.
What types of antimicrobial peptides are present?
Defensins and cathelicidins; Toxic to microbes and recruits leukocytes.
What does lysozyme do?
Hydrolyses peptidoglycan in bacterial cell walls; Produced by epithelial cells of mucous membranes. Also found in lysosomes of phagocytes.
What does lactoferrin do?
Binds free iron to inhibit bacterial growth; Found in same locations as lysozyme.
What is apolactoferrin?
Blocks viral entry by binding lipoproteins, a viral attachment receptor, on epithelial cells.
What do surfactants do?
Bind DIRECTLY to bacteria, viruses, and fungi to increase their phagocytosis; Made by respiratory epithelium, concentrated in alveoli.
What role do antibodies play?
Lead to destruction of microbes through multiple mechanisms; Made by B cells, Located in serum, tears, mucus and breast milk.
What produces plasma proteins?
Constitutively produced by hepatocytes.
What are the three types of plasma proteins? What function do they share?
Acute phase reactants, Mannose binding lectin and complement proteins. They are all opsonins.
What do acute phase reactants do?
They bind to bacterial membranes and apoptotic cells to opsonize them and activate complement cascade. C-reactive proteins(CRP) and serum amyloid P (SAP)
What danger does too many circulating Acute phase reactans present?
Increased risk of heart attack.
What does mannose binding lectin do?
Opsonizes and activates complement. Bind to SURFACE of pathogens.
What do complement proteins do?
Opsonize, recruit phagocytic cells, and lyse by binding directly or indirectly to target surface.
What are the pathways of complement protein?
Alternative, classical and lectin pathways.
Describe the alternative pathway activation.
- C3 is cleaved into C3a and C3b in the serum
2. C3b is bound to pathogen; C3a is an anaphlatoxin (attracts leukocytes)
Describe the classical pathway activation.
- Antibody (IgG or IgM) or CRP/SAP binds to the pathogen’s surface antigen.
- C1 is recruited & and then recruits C4 and C2.
Describe the lectin pathway activation.
- Mannose is the surface antigen.
2. Mannose binding lectin binds mannose, then recruits C2 and C4.
Describe the classical and Lectin pathways once C4 is recruited.
- C4 and C2 are split into C4a, C4b, C2a and C2b.
2 C4b and C2a combine to make and enzyme (C3 convertase). - C3 convertase cleaves C3 into C3a and C3b.
Describe the post activation sequence in the alternative pathway.
- Factor B is cleaved into Bb and Ba.
2. Bb combines with C3b to make C3 convertase.
Why is the cleavage of C3 so important?
C3a is an anaphlatoxin; binds to mast cells, neutrophils and macrophages. C3b is the most powerful opsonin.
