Innate Immunity Flashcards
What are the differences between innate and adaptive immunity?
Innate - fast (secs), lacks specificity, no memory, no change in intensity
Adaptive - slow (days),specificity, immunological memory, changes in intensity
What are the first lines of defence within innate immunity?
Physical barriers
Physiological barriers
Chemical barriers
Biological barriers
What are physical barriers in innate immunity?
Skin
Mucous membranes - mouth, resp tract, etc
Bronchial cilia
What are physiological barriers in innate immunity?
Vomiting
Diarrhoea
Coughing
Sneezing
What are chemical barriers in innate immunity?
Low pH - skin (5.5), stomach (1-3), vagina (4.4)
Antimicrobial molecules - igA (saliva and tears), lysozyme, mucus
What are biological barriers in the innate immune system?
Normal flora in strategic locations - entry points
- nasopharynx, mouth/throat, skin, GI tract, vagina
What are the benefits of normal flora within the body?
- Compete with pathogens for attachment sites and resources
- product antimicrobial chemicals
- synthesise vitamins - K, B12
What normal flora is present in the nasopharynx?
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species
What normal flora is present on the skin?
Gram positive - staph aureus, staph epidermiditis, strep pyogenes
When might normal flora become pathological?
- Displaced from its normal location
- Overgrows if host immunocompromised
- Overgrows when normal flora depleted by antibiotics
Give examples of infections that may be caused from displaced microflora?
UTI - E.coli from the colon enters the urethra
Cellulitis - Staph.aureus enters through a break in the skin
Give 2 examples of infections that occur due to normal flora being depleted by antibiotics?
Clostridium difficile - severe colitis
Candida albicans - vaginal thrush
Patients may be immunocompromised if…
Asplenic or hyposplenic Diabetic AIDS Malignant diseases Chemotherapy
What are the second lines of defence within innate immunity?
Phagocytes, complement system, cytokines
What is the result of activation of the second line of defence?
Inflammation
What are the 3 main phagocytes in innate immunity?
Macrophages
Monocytes
Neutrophils
Give examples of PAMPS on gram negative bacteria.
LPS
Lipoproteins and lipopeptides
Give examples of PAMPS on gram positive bacteria.
Peptidoglycan
Lipoteichoic acids
What is an example of a PRR?
Toll-like receptor
What molecules act as opsonins?
- Complement proteins - C3b
- Antibodies - igG
- Acute phase proteins - CRP, MBL (mannose-binding lectin)
Why are asplenic patients particularly vulnerable to encapsulated bacteria?
These bacteria require opsonisation in order to clear, patients without a spleen have reduced opsonisation.
Give examples of 3 encapsulated bacteria that asplenic patients are at high risk of infection with.
Neisseria meningitis
Strep. Pneumoniae
Haemophilus influenzae
What are the 2 phagocyte killing mechanisms, how do they differ?
Oxygen-dependent pathway (respiratory burst)
= Release of toxic oxygen products - superoxide, H202, hydroxyl radicals.
Oxygen- independent pathway
= proteolytic and hydrolytic enzymes
What are the 2 activating pathways of the complement system?
- MBL - initiated with MBL binds to mannose containing residues on proteins found on microbes
- Alternative - initiated by cell surface microbial constituents (endotoxins on e.coli)
What is the function of C3a and C5a?
Chemoattractants - recruit phagocytes
What is the function of C3b and C5b?
Opsonisation of pathogens
What is the function of C5-9?
Formation of membrane-attack complex (MAC)
Which cytokines are released by macrophages/monocytes?
IL-1
IL-6
TNF-alpha
What effects do IL-1,IL-6 and TNF-alpha have on the liver?
Synthesis and release of opsonins - CRP and MBL
What effects do IL-1,IL-6 and TNF-alpha have on the bone marrow?
Neutrophil mobilisation
How does infection result in an increased temperature?
Macrophage released IL-1, IL-6 and TNF alpha are pyrogens, and signal to the hypothalamus to increase body temperature
What effects do IL-1,IL-6 and TNF-alpha have on the vasculature?
Vasodilation
Vascular permeability
Which patients are likely to have reduced phagocytosis?
- Decreased spleen function
- Decreased neutrophil number - cancer chemotherapy, leukaemia/lymphoma, certain drugs (phenytoin)
- Decreased neutrophil function
Which diseases are associated with decreased neutrophil function?
Chronic granulomatous disease (no respiratory burst due to defective NADPH oxidase)
What effect do corticosteroids have on the immune system?
Immunosuppressants
