L4: Innate Immunity Flashcards
(48 cards)
What factors determine the outcome of host-pathogen relationship?
Infection require patient and pathogen
Pathogen- infectivity –> ability of microbe to establish on or within the host
Patient- host immune response–> Essential in determining outcome of pathogen invasion
Mechanism of action- virulence –> capacity of microbe to do damage to the host
Which groups are most at risk of infection?
Elderly
Children
Pregnant women
Define immune system?
Cells and organs that contribute to the immune defences against infectious and non-infectious conditions (self vs non-self)
Define infectious disease?
When a pathogen suceeds in evading and/or overwhelming the host’s immune defences
What are the key roles of the immune system? How does it do this?
Pathogen recognition–> cell surface and soluble receptors
Containing/ eliminating the infection–> killing and clearance mechanisms
Regulating itself–> minimise damage to host
Remembering pathogens–> prevent disease from recurring
What are the two methods of response in the immune system?
Innate--> Immediate --> prevent microorganisms getting in --> fast (within seconds) --> non specific --> no memory --> no change in sensitivity Adaptive --> long lasting --> Slow (days) --> Specific --> Immunological memory --> Changes in sensitivity
What are the main first lines of defence?
Physical barriers Physiological barriers Chemical barriers Biological barriers --> prevent entry and limit growth
What are the physical barriers?
Skin –> water tight, 1-2m surface area
Mucous membrane–> mouth, respiratory tract, GI tract and urinary tract–> traps pathogens
Bronchial cilia–> trap bacteria in mucous, mucocillary escalator up to mouth
What are the physiological barriers?
Symptoms that the patient presents with
- Diarrhoea
- Vomiting
- Coughing
- Sneezing
In response to pathogen to eliminate pathogen from body
What are the chemical barriers?
Low pH --> point of entry -Skin pH 5.5 -Stomach pH 1-3 -Vagina pH 4.4 Antimicrobial factors
What are the antimicrobial factors?
- IgA (tears, saliva, mucous
- Lysosomes (sebum, perspiration, urine)
- Mucus (mucous membrane)
- Beta-defensins (epithelium)
- Gastric acid + pepsin
What are the biological barriers?
Normal flora
- -> absent from internal organs/tissues
- Compete with pathogens for attachment sites and resources
- Produce antimicrobials and chemicals
- Synthesis vitamins (K, B12 and other B vitamins)
- Immune maturation –> stops immune system producing wrong response
What is the normal flora?
–> non pathological (unless they enter a new environment in the body)
–> strategic locations (nasopharynx, mouth/throat, skin, GI tract, vagina)
Helps normal body functions
What are the normal flora that inhabit the skin?
Staphylococcus aureus Staphylococcus epidermis Streptoccoccus pyogenes Candiba albicans Clostridium perfringens
What are the normal flora that inhabit the nasopharnyx?
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species
How does the normal flora lead to infection?
If it become displaced and enters a new body compartment –> infection
e.g. breaching the skin (burns, cuts, tattoos, injections, surgery), fecal-oral route (foodborne infection), Fecal-perineal-urethral route, poor dental hygiene (gets in through gums)
Which patients are at highest risk of serious infection?
Patients
- without a spleen (asplenic or hyposplenic)
- damaged or prosthetic valves
- previous ineffective endocarditis
What else can causes normal flora to become pathogenic?
Overgrowth and host becomes immuno-compromised (diabetes, AIDS, malignant diseases, chemotherapy)
or
Flora is depleted in mucosal surfaces by antibiotic therapy –> intestine (severe colitis), vagina (thursh)
What is the second line of defence after the barriers have been breached?
Phagocytes and chemicals
–> contain and clear infection
What are the names of the main phagocytes?
Macrophages Monocytes Neutrophils Basophils Eosinophils Natural killer cells Dendritic cells
What are the key features about macrophages?
Present in all organs
Ingest and destroy microbes (phagocytosis)
Present microbial antigens to T cells (adaptive immunity)
Produce cytokines/chemokines
What are monocytes? What is there function?
Precursor to macrophages
Present in blood (5-7%)
Recruited at infection site and differentiate into macrophages
What is the main function of neutrophils?
Present in blood (60% of leukocytes)
Increased during infection
Recruited by chemokines to infection
Ingest and destroy progenitor bacteria (Staph aureus and Strep progenies)
What are the functions of basophil/ mast cells?
Inflammation (vasomodulation)
Allergic response
