The Innate Immune Response Flashcards
(36 cards)
What is the immune system?
Cells and organs that contribute to immune defences against infectious and non-infectious conditions
What is an infectious disease?
When the pathogen succeeds in evading and/or overwhelming the host’s immune defences
What are the roles of the immune system?
- Pathogen recognition (by cell surface and soluble receptors)
- Containing/eliminating the infection (killing and clearance mechanisms)
- Regulating itself (minimum damage to the host)
- Remembering pathogens (to prevent recurrent disease)
What is innate immunity?
- Immediate protection
- Fast (within seconds)
- Lack of specificity
- Lack of memory
- No change in intensity
What is adaptive immunity?
- Longer lasting protection
- Slow (days)
- Highly specific
- Immunologic memory
- Changes in intensity
What factors prevent entry and limit the growth of a pathogen?
First lines of defence
- Physical barriers
- Physiological barriers
- Chemical barriers
- Biological barriers
What are physical barriers?
- Skin
- Mucosal membranes (mouth/respiratory tract/GI tract/Urinary tract)
- Bronchial cilia
What physiological barriers exist in the innate immune response?
- Diarrhoea (in food poisoning)
- Vomiting (food poisoning/hepatitis/meningitis)
- Coughing (pneumonia)
- Sneezing (sinusitis)
What chemical barriers are found in the innate immune response?
- Low pH
- -> skin = 5.5, stomach = 1-3, vagina = 4.4
- Antimicrobial molecules
- – IgA (tears, saliva, mucous membranes)
- – Lysozyme (sebum, perspiration, urine)
- – Mucus (mucous membranes)
- – Beta-defensins (epithelium)
- – Gastric acid + pepsin
What biological barriers exist in the innate immune response?
Normal flora exists of non-pathogenis microbes in strategic locations
- Nasopharynx
- Mouth/throat
- Skin
- GI tract
- Vagina
What are the benefits of a normal flora?
- Compete with pathogens for attachment sites and resources
- Produce antimicrobial chemicals
- Synthesise vitamins (K, B12, other B vitamins)
- Immune maturation
What normal flora are found in the skin?
- Staphylococcus aureus
- Staphylococcus epidermidis
- Streptococcus pyogenes
- Candida albicans
What normal flora are found in the mouth and nasopharynx?
- Streptococcus mutans
- Streptococcus pneumoniae
- Neisseria meningitidis
- Haemophilus species
What normal flora are found in the GI tract?
E. Coli
What has to happen to the flora to cause clinical problems?
Normal flora has to be displaced from its normal location to sterile locations
What breaches the skin integrity?
- Skin loss (burns)
- Surgery
- IV lines
- Skin diseases
- Injection drug users
- Tattooing/body piercing
What other things cause displacement of the normal flora to sterile environments?
- Fecal-oral route (foodborne infection)
- Fecal-perineal-urethral route (UTI, mostly in women)
- Poor dental hygiene/dental work (dental extraction/ gingivitis/ brushing flossing)
- Normal flora overgrows and becomes pathogenic when host is immuno-comprimised
- Normal flora in mucosal surfaces is depleted by antibiotic therapy
What patients are high risk of serious infections relating to the displacement of normal flora?
- Asplenic (and hyposplenic) patients
- Patients with damaged or prosthetic valves
- Patients with previous infective endocarditis
What makes up the second line of defence in the innate immune response?
- Phagocytes
- Compliment system
- Cytokines
What are the main phagocytes and other key cells in innate immunity
- Macrophages
- Monocytes
- Neutrophils (pus)
- Basophils/ mast cells
- Eosinophils
- Natural Killer Cells
- Dendritic Cells
What is the function of the macrophage?
- Present in all organs
- Ingest and destroy microbes (phagocytosis)
- Present microbial antigens to T cells (adaptive immunity)
- Produce cytokines/chemokines
What is the function of the monocyte?
- Present in the blood
- Recruited at infection site and differentiate into macrophages
What is the function of neutrophils?
- Present in the blood
- Increased during infection
- Recruited by chemokines to site of infection
- Ingest and destroy pyogenic bacteria: Staph. aureus and Strep. pyogenes
What is the function of basophils/mast cells?
- Early actors of inflammation (vasomodulation)
- Important in allergic reactions
