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Infection > Innate immunity > Flashcards

Innate immunity Flashcards

1
Q

what is the immune system?

A

Cells and organs that contribute to immune defences against infectious and non infectious conditions (self vs non self)

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2
Q

What is an infectious disease?

A

When a pathogen succeeds in evading &/or overwhelming the host immune defences

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3
Q

What are main roles of the immune system?

A 
Pathogen recognition (cell surface and soluble receptors) 
Containing/eliminating the infection (killing and clearance mechanisms 
Regulating itself (minimum damage to host (resolution)
Remembering pathogens (preventing disease from returning)
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4
Q

Summarise innate immunity

A

Immediate protection
- fast (within seconds)
Lack of specificity and memory
No change in intensity with repeated infection

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5
Q

What are the first lines of defence in innate immunity?

A
  • physical barriers
  • Physiological barriers
  • Chemical barriers
  • Biological barriers
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6
Q

List the physical barriers of the innate immune system

A
  • skin
  • mucous membranes: mouth, RT, GIT, UT (array of different microbial substances)
  • Bronchial cilia (expel trapped microorganisms)
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7
Q

List the physiological barriers of the innate immune system

A
  • Diarrhoea
  • Vomiting: food poisoning, Hep, meningitis
  • Coughing: Pneumonia
  • Sneezing: sinusitis
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8
Q

List the Chemical barriers of the innate immune system

A
  • Low pH: skin (5.5), Stomach (1-3), Vagina (4.4)
  • Antimicrobial molecules (IgA- tears, saliva, mucous membrane, Lysozyme- sebum, perspiration, urine, Mucus- mucous membrane, Beta-defensins- epithelium, Gastric acid & pepsin- stomach)
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9
Q

List the Biological barriers of the innate immune system

A

Normal flora: normal non-pathogenic microbes

Strategic locations: nasopharynx, mouth/throat, skin, GIT, vagina. Absent in internal organs/tissues

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10
Q

What are the benefits of the normal flora in the human body?

A

Compete with pathogens for attachement sites and resources
Produce antimicrobial chemicals
Synthesis vitamins (K, B12, other B- vitamins)

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11
Q

Give examples of normal flora associated with the skin

A

Staphylococcus aureus, stah epidermis, strep pyrogenes, candida albicans and clostridium perfingens

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12
Q

Give examples of normal flora associated with the nasopharynx

A

Streptococcus pneumoniae, neisseria meningitidis, haemophillus species

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13
Q

List circumstances which may lead to the breaching of skin integrity and therefore infection

A

Skin loss (burns)
Surgery –> anesthesia or infection at incision site
injection drug users
IV lines –> Central venous line is most dangerous

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14
Q

What infection is transmitted via the feacal-perineal-urethral route?

A

UTI

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15
Q

Why is poor dental hygiene/poor dental work an infection risk?

A

Common cause of harmless bacteraemia : dental extraction, gingivitis, brushing/flossing
Can lead to serious infections in high risk patients:
- Asplenic (or hyposplenic) pts.
- Pts with damaged or prosthetic valves
- Pts with previous infective endocarditis

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16
Q

Give some examples of conditions that can lead a host to become immunocompromises

A

Diabetes micro-vascular disease, immunocompromised, decrease in immune cells
AIDS
Malignant diseases (cancer/treatment)
Chemotherapy (mucositis) –> disrupts function therefore normal flora enters circulation

17
Q

What occurs in a Clostridium difficile infection?

A

The normal flora in the intestine is disrupted leading to a increase in the amount of c.diff in the intesine –> severe colitis

18
Q

What can happen in the vagina if the normal flora is disrupted by abx?

A

Candida albicans = Thrush

19
Q

What are the second lines of defence in innate immunity?

A

Phagocytes
Chemicals
Inflammation

Factors that will contain and clear infection

20
Q

List the different innate immune cells

A 
Macrophages
Monocytes 
Neutrophils 
Basophils/Mast cells
Eosinophils 
NK cells
Dendritic cells
21
Q

List the functions of macrophages

A

Present in all organs
Ingest and destroy microbes via phagocytosis
professional antigen presenting cells (T-cells)
Produce cytokines and chemokines
Long lived and can generate more granules if needed (unlike neutrophils)

22
Q

What are monocytes?

A

Present in the blood, recruit to the site of infection and differentiate into macrophages

23
Q

List the functions of neutrophils

A

Present in the blood (60% of blood leukocytes), arrival is 1st even of inflammatory response
increased during infection, exclusion from healthy tissue
Phagocytes
Recruited by chemokines to the site of infection
Ingest and destroy pyogenic bacteria (Staph aureus and strep pyogenes)
Specialised for working in anaerobic conditions

24
Q

List the functions of basophil and Mast cells

A

Early actors of inflammation (vasomodulation)
Important in allergic response (contain histamine)
Protection of mucosal surfaces (mast cells)

25
Q

List the functions of Eoisinophils

A

Defence against multi-cellular parasites (worms) and important in allergy response

26
Q

List the functions of Natural Killer cells

A

Provides innate immunity against intracellular infections

Kill all abnormal host cells (virus infected or malignant cells)

27
Q

List the functions of dendritic cells

A

Present microbial antigens to T-cells (acquired immunity)

28
Q

What are pathogen-associated molecular patterns?

A

PAMPs, are molecules associated with groups of pathogens on the microbe, they are recognized by cells of the innate immune system. include microbial structures (Carbohydrate, proteins, nucleic acids)

29
Q

What are Pathogen Recognition Receptors

A

Toll-like receptors (not necessarily on the cell surface, some inside cell as viruses can invade cell) that recognise PAMP’s
Located on the phagocytes

30
Q

Give an example of a gram negative PAMP and the cognate PRRs

A

LPS - TLR4

Lipoproteins and Lipopptides - TLR2

31
Q

Give an example of a gram positive PAMP and the cognate PRRs

A

Peptidoglycan - TLR2

Lipoteichnoic acids - TLR4

32
Q

Give an example of a All mycobacteria PAMP and the cognate PRRs

A

Lipoarabinomannan – TLR2

mannose rich glycans

33
Q

Give and example of bacterial flagella PAMP and the cognate PRRs

A

Flagellas - TLR5

34
Q

Describe the opsonisation of a microbe

A

The coating of a microorganism by antibodies or complement to render it recognisable as foreign by phagocytes, thus enhancing phagocytosis.

35
Q

Give examples of opsonins

A

Complement of proteins: C3b, C4b
Antibodies: IgG and IgM
Acute phase proteins: CRP and Mannose binding Lectin (MBL)

36
Q

What bacteria are opsonins essential for clearing?

A

Encapsulated

37
Q

Describe the process of phagocytosis

A
  1. chemotaxis & adherence of microbe to phagocyte
  2. ingestion of microbe by phagocyte
  3. formation of phagosome
  4. fusion of the phagosome with a lysosome to form a phagolysosome
  5. Digestion of ingested material by enzymes
  6. formation of residual body containing indigestaible material
  7. damage of waste materials
38
Q

What are the two phagocytic intracellular killing mechanisms?

A 
Oxygen-dependent pathway (respiratory burst) 
Oxygen independent pathways: 
-Lysozyme
-lactoferrin or transferrin
-cationic proteins 
- proteolytic and hydrolytic enzymes

Infection (4 decks)

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