3. Innate Immunity Flashcards
What 3 factors determine the outcome of the host-pathogen relationship?
Host’s immune response
Infectivity
Virulence
What is the definition of the immune system?
Cells and organs that contribute to immune defences against infections and non-infectious conditions
What is the definition of an infectious disease?
When the pathogen succeeds in evading and/or overwhelming the host’s immune defences
What are the 4 main roles of the immune response?
Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens
What are the 4 main characteristics of the innate immune system?
Fast
Lack of specificity
Lack of memory
No change in intensity
What are the 4 main characteristics of the adaptive immune system?
Slow
Specificity
Immunologic memory
Changes in intensity
What are the main physical barriers of the first line if defence in the innate immune system?
Skin
Mucous membranes eg mouth, GI tract
Bronchial cilia
What are the main physiological barriers of innate immunity first line defence?
Diarrhoea
Vomiting
Coughing
Sneezing
What are the main chemical barriers in innate immunity first line defence?
Low pH eg 4.4 vagina
Antimicrobial molecules eg IgA in tears, saliva and mucous membranes
What are the main biological barriers in innate immunity first line defence?
Normal flora:
Nonpathogenic microbes
Strategic locations - eg skin, vagina
Absent in internal organs/tissues
Give an example of a normal bacteria that inhabits the skin
Staphylococcus aureus
Give an example of 2 normal bacteria that inhabits the nasopharynx
Streptococcus pneumoniae
Neisseria meningitidis
Name 4 routes by which normal flora can be displaced from its normal location to a sterile location and cause infection
Breaching skin integrity
Fecal-oral
Fecal-perineal-urethral
Poor dental hygiene/dental work
What is a common cause of harmless bacteraemia?
Poor dental hygiene/dental work
What different groups of patients are at high-risk of serious infections?
Asplenic/hyposplenic patients
Damaged or prosthetic valves
Previous infective endocarditis
Immune-compromised eg diabetes, AIDS, chemo (decreases neutrophil number), malignant diseases
Patients with decreased neutrophil function eg chronic granulomatous disease (no respiratory burst)
Give 2 infections that can occur when normal flora is depleted by antibiotics
Clostridium difficile - severe colitis - intestine
Candida albicans - thrush - vagina
What are the 3 main phagocytic cells that are important in the second line defence of the innate immune system?
Macrophages
Monocytes
Neutrophils
Give a structure found on the surface of microbes that allow their recognition by the innate immune cells?
PAMPs
Give the name of the receptors found on the surface of phagocytes that recognise microbes and an example of one
PRRs eg TLR2 or TLR4
What is opsonisation?
Coating of microbe surfaces with coating proteins called opsonins. Leads to enhanced attachment of phagocytes (neutrophils) and clearance of microbes
What are opsonins essential in?
Clearing encapsulated bacteria
Name 3 classes of opsonins and 2 examples of each
Complement proteins eg C3b, C4b
Antibodies eg IgG, IgM
Acute phase proteins eg CRP, MBL
What are the two main pathways of the phagocyte intracellular killing mechanisms?
Oxygen-dependent pathway (respiratory burst) eg NO
Oxygen-independent pathway eg lysozyme
What are the two activating pathways of the complement system? How are they initiated?
Alternative pathway - initiated by cell surface microbial constituents
MBL pathway - initiated by MBL binding to mannose containing residues of proteins found on microbes
