Innate immunity Flashcards
(38 cards)
what is the immune system?
Cells and organs that contribute to immune defences against infectious and non infectious conditions (self vs non self)
What is an infectious disease?
When a pathogen succeeds in evading &/or overwhelming the host immune defences
What are main roles of the immune system?
Pathogen recognition (cell surface and soluble receptors) Containing/eliminating the infection (killing and clearance mechanisms Regulating itself (minimum damage to host (resolution) Remembering pathogens (preventing disease from returning)
Summarise innate immunity
Immediate protection
- fast (within seconds)
Lack of specificity and memory
No change in intensity with repeated infection
What are the first lines of defence in innate immunity?
- physical barriers
- Physiological barriers
- Chemical barriers
- Biological barriers
List the physical barriers of the innate immune system
- skin
- mucous membranes: mouth, RT, GIT, UT (array of different microbial substances)
- Bronchial cilia (expel trapped microorganisms)
List the physiological barriers of the innate immune system
- Diarrhoea
- Vomiting: food poisoning, Hep, meningitis
- Coughing: Pneumonia
- Sneezing: sinusitis
List the Chemical barriers of the innate immune system
- Low pH: skin (5.5), Stomach (1-3), Vagina (4.4)
- Antimicrobial molecules (IgA- tears, saliva, mucous membrane, Lysozyme- sebum, perspiration, urine, Mucus- mucous membrane, Beta-defensins- epithelium, Gastric acid & pepsin- stomach)
List the Biological barriers of the innate immune system
Normal flora: normal non-pathogenic microbes
Strategic locations: nasopharynx, mouth/throat, skin, GIT, vagina. Absent in internal organs/tissues
What are the benefits of the normal flora in the human body?
Compete with pathogens for attachement sites and resources
Produce antimicrobial chemicals
Synthesis vitamins (K, B12, other B- vitamins)
Give examples of normal flora associated with the skin
Staphylococcus aureus, stah epidermis, strep pyrogenes, candida albicans and clostridium perfingens
Give examples of normal flora associated with the nasopharynx
Streptococcus pneumoniae, neisseria meningitidis, haemophillus species
List circumstances which may lead to the breaching of skin integrity and therefore infection
Skin loss (burns)
Surgery –> anesthesia or infection at incision site
injection drug users
IV lines –> Central venous line is most dangerous
What infection is transmitted via the feacal-perineal-urethral route?
UTI
Why is poor dental hygiene/poor dental work an infection risk?
Common cause of harmless bacteraemia : dental extraction, gingivitis, brushing/flossing
Can lead to serious infections in high risk patients:
- Asplenic (or hyposplenic) pts.
- Pts with damaged or prosthetic valves
- Pts with previous infective endocarditis
Give some examples of conditions that can lead a host to become immunocompromises
Diabetes micro-vascular disease, immunocompromised, decrease in immune cells
AIDS
Malignant diseases (cancer/treatment)
Chemotherapy (mucositis) –> disrupts function therefore normal flora enters circulation
What occurs in a Clostridium difficile infection?
The normal flora in the intestine is disrupted leading to a increase in the amount of c.diff in the intesine –> severe colitis
What can happen in the vagina if the normal flora is disrupted by abx?
Candida albicans = Thrush
What are the second lines of defence in innate immunity?
Phagocytes
Chemicals
Inflammation
Factors that will contain and clear infection
List the different innate immune cells
Macrophages Monocytes Neutrophils Basophils/Mast cells Eosinophils NK cells Dendritic cells
List the functions of macrophages
Present in all organs
Ingest and destroy microbes via phagocytosis
professional antigen presenting cells (T-cells)
Produce cytokines and chemokines
Long lived and can generate more granules if needed (unlike neutrophils)
What are monocytes?
Present in the blood, recruit to the site of infection and differentiate into macrophages
List the functions of neutrophils
Present in the blood (60% of blood leukocytes), arrival is 1st even of inflammatory response
increased during infection, exclusion from healthy tissue
Phagocytes
Recruited by chemokines to the site of infection
Ingest and destroy pyogenic bacteria (Staph aureus and strep pyogenes)
Specialised for working in anaerobic conditions
List the functions of basophil and Mast cells
Early actors of inflammation (vasomodulation)
Important in allergic response (contain histamine)
Protection of mucosal surfaces (mast cells)
