Innate Immune System Flashcards
Define infectivity
Infectivity - ability of microbe to establish itself in the host
Define virulence
Virulence - capacity of the microbe to cause tissue damage
Define the immune system
Immune system =
Cells and organs (eg spleen) that contribute to immune
defences against infectious and non-infectious
conditions (self vs non-self) Cells
Immune system can also recognise non infections conditions eg modified self cells
Immune system can recognise/differentiate self/non self
Define infectious disease
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 = Cell surface and soluble receptors
Foreign microbes cant get anywhere
Containing/eliminating the infection = Killing and clearance mechanisms
Need to be contained so it does not become systemic infection
Want infection to be continues otherwise sepsis
Immune system can contain and deal with infection
Regulating itself = Minimum damage to host (resolution)
Deactivated when threat stopped
Remembering pathogens = Preventing the disease from recurring
Immunisation - remember the microbe
Modified microbe - start immune response, - memory when real microbe encountered - already have the antibodies
What is innate immunity
Innate - any microbe has to pass innate immunity
Need to find a path of entry ofpathogen
If it gets through innate - faces specific defences
Innate gives immediate protection - fast
Innate has receptors that have receptors that recognise groups of microbes but very efficient lacks memory - therefore no change in intensity
What is adaptive immunity
Adaptive
Would not have adapted if innate not activated
Link between innate - adaptive
Need to activate innate to active adaptive
Adaptive - long lasted - antibodies stay in the blood
But slow
Very specific - can distinguish between different classes of microbes - can recognisedifferent categories of microbes within same group - eg 9 different strains of strep pneumoniae - can recognise the same strain on different epitomes - antigen can recognise this
The morey0u are exposed to same microbe - the Bette =r the immune response is BUT IN THE CASE OF FLU - FLU virus changes all the time.0 scone time = different type of virus -
What are the physical barriers to pathogen entry
Skin = physical barrier
Outer part of skin has no blood -
Mucous memb - a lot of secretion - immune - gals malt etc - produces best local response - present in mouth, respiratory tract, Gi tract, urinary tract
Inetsact with environment but provide protection
What are physiological barie4s to pathogen entry
- Diarrhoea
- Food poisoning
- Vomiting
- Food poisoning
- Hepatitis
- Meningitis
- Coughing
- Pneumonia
- Sneezing
- Sinusitis
What are chemical barriers to pathogen entry
Low pH
Microbesv sensitive to low ph
Staph etc cant grow on skin bc of ph
Stomach low.- acidic - kills anything ingested so nothing gets into intestine
Vagina ph maintained by lactobacillus - produce lactic acid - so bacteria and fungi cannot grow
Antimicrobial molecules
Mucus membrane - form of antibody called IgA produced. IGA binds to microbes and prevents them attaching to membranes etc - in tears, saliva, mucous membrane
Lysozymes - breaks bacterial wall - sebum, perspiration urine
Musus - sticky - cleared by cilia
Beta defensins - epithelium
Epithelium has many antimicrobial molecules
Gastricacid + pepsin- acidic environment used to clear molecules
Wha5 ar the biological Barrie’s to pathogen entry
- Normal flora
- Non pathogenic microbes
- Strategic locations
- Nasopharynx
- Mouth/Throat
- Skin
- GI tract
- Vagina (lactobacillus spp)
- Absent in internal organs/tissues
- Benefits
- Compete with pathogens for attachment sites and resources.
- Produce antimicrobial chemicals
- Synthesize vitamins (K, B12, other B vitamins).
What are examples of normal flora?
- The skin
- Staphylococcus aureus (week 1, case 1)
- Staphylococcus epidermidis
- Streptococcus pyogenes
- Candida albicans
- Clostridium perfringens
- The nasopharynx
- Streptococcus pneumoniae (week 3, case 2)
- Neisseria meningitidis (week 3, lecture case)
- Haemophilus species
How can normal flora cause infection?
Normal flora is displaced from its normal location to sterile location • Breaching the skin integrity • Skin loss (burns) • Surgery • Injection drug users • IV lines
- Fecal-oral route
- Foodborne infection
- Fecal-perineal-urethral route
- Urinary tract infection (women)
• Poor dental hygiene/dental work
Common cause of harmless bacteraemia
Bacteria in blood
• Dental extraction • Gingivitis • Brushing/Flossing
⇒ Serious infections in high-risk patients • Asplenic (and hyposplenic) patients • Patients with damaged or prosthetic valves • Patients with previous infective endocarditis -> Antibiotic prophylaxis (UK?)
• Normal flora overgrows and becomes pathogenic when
host becomes immuno-compromised
• Diabetes (session 3, case 2)
• AIDS - drop in t helper cell no
• Malignant diseases - cancer could infiltrate lymphoid organ
• Chemotherapy (mucositis)
- When normal flora is depleted by antibiotics
- Intestine -> severe colitis (Clostridium difficile) • Vagina -> thrush (Candida albicans)
What are macrophages
Present in all organs Ingest and destroy microbes (Phagocytosis) Present microbial antigens to T cells (adaptive immunity) Produce cytokines/chemokines
What are monocytes
Present in the blood (5-7%) Recruited at infection site and differentiate into macrophages
