Innate Immunity

Question 1

Immune system definition

Answer 1

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

Question 2

Infectious disease definition

Answer 2

When pathogen succeeds in evading/overwhelming the hosts immune defences

Question 3

Roles of immune system

Answer 3

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

Question 4

Innate immunity features

Answer 4

Fast
Lack specificity
Lack memory
No change in intensity

Question 5

Adaptive immunity features

Answer 5

Slow
Specific
Immunological memory
Changes intensity (depending on exposure)

Question 6

First lines of defence

Answer 6

Physical, physiological, chemical, biological

Prevent entry and growth

Question 7

Physical barriers

Answer 7

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

Question 8

Physiological barriers

Answer 8

Diarrhoea
Vomiting
Coughing
Sneezing

Question 9

Chemical barriers

Answer 9

Low pH (stomach, skin)

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

Question 10

Biological barriers

Answer 10

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

Question 11

Benefits of biological barriers

Answer 11

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

Question 12

When do normal flora become pathogenic location wise

Answer 12

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

Question 13

Other reasons why normal flora can become pathogenic

Answer 13

Overgrowth and immunocompromised (diabetes, AIDS, chemo)

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

Question 14

High risk patients

Answer 14

Old
Young
Pregnant
Aspen if
Damaged/prosthetic valves
Previous endocarditis

Question 15

Second line defence innate immunity

Answer 15

Phagocytes and chemicals causing inflammation

Contain and clear infection

Question 16

Macrophage

Answer 16

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

Question 17

Monocytes

Answer 17

Immature macrophage - in blood

Differentiate into macrophage

Question 18

Neutrophils (pus)

Answer 18

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

Question 19

Basophils/mast cells

Answer 19

Inflammation

Allergic response

Question 20

Eosinophils

Answer 20

Parasite protection (worms)

Question 21

Natural killer cells

Answer 21

Kill abnormal host cells (malignant or virus infected)

Question 22

Dendritic cells

Answer 22

Present microbial antigens to T cells - queen of adaptive immunity

Result in acquired immunity

Question 23

How are pathogens recognised by phagocytes

Answer 23

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

Phagocytes have PRRS - pathogen recognition receptor

Question 24

What PRR recognises LPS

Answer 24

TLR4 (toll like receptor 4)

Question 25

Can 1 phagocyte receptor recognise only one type of bacteria?

Answer 25

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

Question 26

What is opsonisation of microbes

Answer 26

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

Question 27

What are opsonins essential for

Answer 27

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

Question 28

Examples of opsonins

Answer 28

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

Question 29

Phagocytes intracellular killing mechanisms

Answer 29

Oxygen dependent pathway (respiratory burst) = toxic O2 products, hydrogen peroxide, hydroxyl radical, nitric oxide Oxygen independent pathways - lysozyme, transferrin, proteolytic enzymes, cationic proteins

Question 30

What does the complement system activate (C3a and C5a)

Answer 30

Recruitment of phagocytes

Question 31

What does C3b complement system activate

Answer 31

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

Question 32

What does C5-C9 complement pathway activate

Answer 32

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

Question 33

Macrophage derived cytokines

Answer 33

TNFa, IL-1, IL-6

Question 34

Actions of macrophage derived cytokines

Answer 34

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

Question 35

Significance of vasodilation and permeability

Answer 35

More monocytes and neutrophils can enter to go to infection

Question 36

When is phagocytosis reduced

Answer 36

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