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Infection 2023 > Innate Immunity > Flashcards

Innate Immunity Flashcards

1
Q

Immune system definition

A

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

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2
Q

Infectious disease definition

A

When pathogen succeeds in evading/overwhelming the hosts immune defences

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3
Q

Roles of immune system

A 
Recognise pathogen (receptors)
Contain/eliminate infection 
Regulate itself (minimal host damage)
Remember pathogens (prevent reoccurrence of disease)
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4
Q

Innate immunity features

A

Fast
Lack specificity
Lack memory
No change in intensity

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5
Q

Adaptive immunity features

A

Slow
Specific
Immunological memory
Changes intensity (depending on exposure)

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6
Q

First lines of defence

A

Physical, physiological, chemical, biological

Prevent entry and growth

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7
Q

Physical barriers

A

Skin, mucosal membranes (mouth, respiratory tract, GI tract), Cilia

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8
Q

Physiological barriers

A

Diarrhoea
Vomiting
Coughing
Sneezing

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9
Q

Chemical barriers

A

Low pH (stomach, skin)

Anti microbial: 
IgA - tears, mucus membrane
Lysozyme 
Mucus 
Beta defensins
Gastric acid + pepsin
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10
Q

Biological barriers

A

Normal flora - non pathogenic microbes in portal entry (mouth, vagina, skin)
NOT PRESENT IN INTERNAL ORGANS

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11
Q

Benefits of biological barriers

A

Compete with pathogens for attachment sites and nutrients
Produce antmicrobials
Synthesise viatmins (k, b12, b vitamins)
Immune maturation

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12
Q

When do normal flora become pathogenic location wise

A 
When displaced from normal location eg:
breach of skin
fecal-oral
fecal-urethral
Poor dental hygiene 
Dental work
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13
Q

Other reasons why normal flora can become pathogenic

A

Overgrowth and immunocompromised (diabetes, AIDS, chemo)

Norma flora depleted by antibiotics (cause thrush from Candida Albicans)

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14
Q

High risk patients

A 
Old
Young
Pregnant
Aspen if
Damaged/prosthetic valves
Previous endocarditis
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15
Q

Second line defence innate immunity

A

Phagocytes and chemicals causing inflammation

Contain and clear infection

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16
Q

Macrophage

A

All organs
Ingest and destroy
Present antigens to T cells
Produce cytokines and chemokines

17
Q

Monocytes

A

Immature macrophage - in blood

Differentiate into macrophage

18
Q

Neutrophils (pus)

A

Blood
Increased during infection (usually bacterial)
Recruited by chemokines
Ingest and destroy pyogenic bacteria (staph aureus, strep pyrogenes)

19
Q

Basophils/mast cells

A

Inflammation

Allergic response

20
Q

Eosinophils

A

Parasite protection (worms)

21
Q

Natural killer cells

A

Kill abnormal host cells (malignant or virus infected)

22
Q

Dendritic cells

A

Present microbial antigens to T cells - queen of adaptive immunity

Result in acquired immunity

23
Q

How are pathogens recognised by phagocytes

A

Pathogens have PAMPS (pathogen associated molecular patterns) - carbs, nucleic acid, lipids, proteins

Phagocytes have PRRS - pathogen recognition receptor

24
Q

What PRR recognises LPS

A

TLR4 (toll like receptor 4)

25
Q

Can 1 phagocyte receptor recognise only one type of bacteria?

A

No, sometimes 1 receptor can sometimes recognise gram negative and gram positive bacteria

26
Q

What is opsonisation of microbes

A

Coating a protein on microbe leading to enhanced attachment of phagocyte as phagocyte has opsonin receptor

27
Q

What are opsonins essential for

A

Clearing encapsulated bacteria (NHS - neisseria meningitidis, haemophilus influenzae streptococcus pneumoniae)

28
Q

Examples of opsonins

A

Complement proteins - C3b
Antibodies - IgG
Acute phase proteins - CRP

29
Q

Phagocytes intracellular killing mechanisms

A

Oxygen dependent pathway (respiratory burst) = toxic O2 products, hydrogen peroxide, hydroxyl radical, nitric oxide

Oxygen independent pathways - lysozyme, transferrin, proteolytic enzymes, cationic proteins

30
Q

What does the complement system activate (C3a and C5a)

A

Recruitment of phagocytes

31
Q

What does C3b complement system activate

A

Opsonisation of pathogens (coat in protein to allow phagocytes to bind)

32
Q

What does C5-C9 complement pathway activate

A

Killing of pathogens via membrane attacking complex (holes in membrane)

33
Q

Macrophage derived cytokines

A

TNFa, IL-1, IL-6

34
Q

Actions of macrophage derived cytokines

A

Liver - opsonins eg CRP
Bone marrrow - neutrophil mobilisation
Hypothalamus - increased temp
Blood vessels - vasodilation, vascular permeability, express adhesion molecules to attract neutrophils

35
Q

Significance of vasodilation and permeability

A

More monocytes and neutrophils can enter to go to infection

36
Q

When is phagocytosis reduced

A 
Decreased spleen (hyposplenic/asplenic), 
decreased neutrophils (chemo, drugs, leukaemia), decreased neutrophil function

Infection 2023 (29 decks)

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