Lecture 4 new Flashcards
(40 cards)
Define the immune system:
Cells and organs that contribute to immune defences against infectious and non-infectious conditions (cancer)
Define infectious disease:
When the pathogen succeeds in evading and/or overwhelming the host’s immune defences
What is infectivity?
Ability of microorganisms to establish itself within the host or on the host
What are the roles of the immune system?
PCRR
Pathogen recognition- cell surface and soluable receptors
Containing/eliminating infection (killing and clearance mechanisms)
Regulating itself- minimum damage to host, otherwise you develop autoimmune
Remembering pathogens- prevent the disease from recurring
What are the two types of defence?
Innate immunity
- fast
- lack of specificity
- lack of memory
- no change in intensity
Adaptive immunity
- slow
- specific
- immunologic memory
- changes in intensity
What are the 1st line defences? (innate immunity)
Barriers to stop pathogen entering
- physical barriers
- physiological barriers
- chemical barriers
- biological barriers
What are the physical barriers?
- skin
- mucous membranes of mouth/ resp tract/ GI tract/ urinary tract
- bronchial cilia (beat to expel trapped microbes in mucous)
What are the physiological barriers?
- diarrhoea (food poisoning)
- vomiting (food poisoning/hepatitis/meningitis)
- coughing (pneumonia)
- sneezing (sinusitis)
What are the chemical barriers?
Low pH: skin 5.5, stomach 1-3, vagina 4.4 Antimicrobial molecules: -IgA (tears/saliva/mucous membrane) -lysozyme (sebum/perspiration/urine) -mucous (mucous membrane) -beta-defensins (epithelium) -gastric acid and pepsin (endopeptidase)
What are biological barriers?
Normal flora
-non pathogenic microbes (found in nasopharynx, mouth, throat, skin, GI tract, vagina)
Where are normal flora absent?
In internal organs/tissues
What are the benefits of normal flora?
-compete with pathogens for attachment sites and resources
-produce antimicrobial chemicals
-synthesise vitamins K, B12, and other B vitamins
-immune maturation
(normal flora can become pathogenic)
Give some examples of normal flora that inhabit the skin:
- staphylococcus aureus
- staphylococcus epidermidis
- streptococcus pyogenes
- candida albicans
- clostridium perfringens
Give some examples of normal flora that inhabit the nasopharynx:
- streptococcus pneumoniae
- neisseria meningitidis
- haemophilus species
How is normal flora displaced from its normal location?
Breaching skin integrity
- skin loss (burns)
- surgery
- IV lines
- skin diseases
- injection drug users
- tattooing/body piercing
Fecal-oral route
-foodbourne infection
Fecal-perineal-urethral route
-UTI in women
Poor dental hygiene/dental work
- dental extraction
- gingivitis (gum disease)
- brushing/flossing
What is the perineum?
The space between the anus and scrotum in the male and between the anus and the vulva in the female
What are some high risk patients susceptible to serious infections?
- asplenic/hyposplenic patients
- patients with damaged/prosthetic valves
- patients with previous infective endocarditis (infection of of the endocardium- the inner lining of the heart)
What may cause normal flora to overgrow and become pathogenic when host is immunocomprimised?
- diabetes
- AIDS
- malignant diseases
- chemotherapy
What conditions cause the flora in mucosal surfaces to be depleted by antibiotic therapy?
- severe colitis (intestine): clostridium difficile
- thrush (vagina): candida albicans
What are the second lines of defences that contain and clear the infection?
- phagocytes
- chemicals
- inflammation
What are the main types of phagocytes?
- macrophages
- monocytes
- neutrohpils (pus)
What is the function of a macrophage?
- present in all organs
- ingest and destroy microbes via phagocytosis
- present microbial antigens to T cells
- produce cytokines/chemokines
What is the function of monocytes?
- present in blood
- recruited at infection site and differentiate into macrophages
What is the function of neutrophils?
- present in blood (60% of blood leukocytes)
- increased during in infection
- recruited by chemokines to site of infection
- ingest and destroy pyogenic bacteria (Staph. aureus, Strep.pyogenes)
