Lecture 10

Question 1

how exotoxins damage host cells, an example of a bacterium and the disease they cause

Answer 1

1. electrolyte secretion - Vibrio cholerae - Diarrhoea
2. necrosis - Staphylococcus aureus - the death of host cells (e.g. leukocidin production)
3. apoptosis (programmed cell death) - Escherichia coli - triggered by Shiga toxins
4. nerve synapse inhibition - Clostridium species - nerve terminals are blocked and muscles can’t contract (paralysis, tetani, botulism)
5. superantigens - Staphylococcus aureus - trigger cytokine release e.g. toxic shock syndrome toxin (can be lethal)

Question 2

how endotoxins damage host cells and an example of a bacterium

Answer 2

lipopolysaccharide (LPS) in the cell wall of Gram Negative bacteria causes an inflammatory cascade (TLR4 agonist)

Question 3

how cell wall fragments (other than LPS) damage host cells and an example of a bacterium

Answer 3

Lipoteichoic acid in Gram-positive bacteria causes an inflammatory cascade

Question 4

how hydrolytic enzymes damage host cells and an example of a bacterium

Answer 4

matrix remodelling/tissue digestion (allow bacteria to spread through tissues), e.g. using hyaluronidase and proteases from Staphylococcus aureus

Question 5

how inhibition of secretory products damages host cells and an example of a bacterium

Answer 5

1. Inhibition of stomach acid secretion by Helicobacter pylori
2. Inhibition and degradation of digestive enzymes by Giardia lamblia (protozoan)

Question 6

how invasion and intracellular multiplication damage host cells and an example of a bacterium

Answer 6

damage/lysis of to host tissue, immune evasion, certain pathogens infect cells to get to another place by using them as trogen horses, e.g. malaria parasite to get to the brain. viruses, parasites (malaria), bacteria (salmonella, mycobacterium tuberculosis)

Question 7

how induction of autoantibodies damage host cells and an example of a bacterium

Answer 7

immune damage to host tissue (microbial antigens similar to the host antigens evoke an autoantibody response) e.g. Rheumatic fever by Streptococcus pyogenes

Question 8

how mutation damage host cells and an example of a bacterium

Answer 8

uncontrolled cell growth (tumour), some viruses carry oncogenes which when inserted into DNA cause tumours. removal of virus doesn’t remove tumour

Question 9

how obstruction damage host cells and an example of a bacterium

Answer 9

blocking blood or lymphatic vessels, occurs particularly with parasites which form large masses, e.g. hydatid cysts of the parasite Echinococcus granulosus (tape worm)

Question 10

host responses to microorganisms

Answer 10

1. inflammation (non-specific, basic, primitive protection against invading pathogens)
2. immune response (specific)

Question 11

types of tissue injury (not mechanisms)

Answer 11

ischaemic, physical, chemical, infectious, immunological

Question 12

suffix for inflammation

Answer 12

-itis

Question 13

what is pyrexia?

Answer 13

fever

Question 14

cardinal signs of inflammation

Answer 14

heat, redness, swelling, pain, loss of function (context dependent - where’s being affected)

Question 15

what is suppuration?

Answer 15

injury to solid tissue (e.g. kidney, brain, dermis, liver) and the causal agent is a pyogenic (pus-forming) organism

Question 16

what is an abscess?

Answer 16

tissue injury localised by a fibroblastic boundary and has a necrotic pus-filled centre

Question 17

what is an ulcer?

Answer 17

inflammatory lesions on the epithelial surfaces (pus forms, result of neutrophil phagocytosis)

Question 18

what is cellulitis?

Answer 18

an inflammatory reaction spreading through CT planes

Question 19

Inflammatory process:

Answer 19

1. release of mediators from activated cells and plasma 2. vasodilation, increased vasopermeability, abnormal movement of fluid and plasma proteins into extravascular sites. hyperaemia (increase blood flow) causing redness, heat and swelling (related to capillaries). increased outflow of fluid due to increase in the net pressure in the capillaries and post capillary venules
2. migration and activation of leukocytes in response to attractant substances

Question 20

role of pre-capillary sphincters during acute inflammation

Answer 20

opens during acute inflammation to enable hyperaemia in the capillaries and for WBC’s to be fit in them (capillaries too narrow to allow WBC’s in with normal blood flow)

Question 21

during infection how quickly and often does acute inflammation occur?

Answer 21

quickly and continuously

Question 22

Systemic effects of inflammation:

Answer 22

a) pyrexia (fever) - mediated by cytokine IL-1 from monocytes and macrophages
b) leukocytosis - increased production and release of neutrophils and monocytes from bone marrow
c) acute phase proteins - increased production of liver proteins which limit tissue damage and resolve infection and inflammation, e.g. fibrinogen and complement proteins
d) endocrine changes - increased production of glucocorticoid and other steroid hormones in response to stress. other endocrine organs may be affected when physiological stress is severe or sustained
e) uptake of debris by dendritic cells (APC) which move to the lymph nodes via lymphatic vessels

Question 23

what drug can reduce pyrexia?

Answer 23

paracetamol

Question 24

function of primary lymphoid organs and examples

Answer 24

production of lymphocytes - bone marrow (B lymphocytes), thyroid (T lymphocytes)

Question 25

function of secondary lymphoid organs and examples

Answer 25

housing of matured lymphocytes from primary organs, filter foreign matter out of the body fluids and are the site of innate immune responses to foreign antigens - spleen, lymph nodes, tonsils, adenoids, Peyer’s patches (in intestine), skin, appendix

Question 26

how to B and T cells travel around the body?

Answer 26

blood and lymph

Question 27

how specialised are APC’s, what cells are APC’s and what is their function?

Answer 27

very specialised - macrophages, dendritic cells, Langerhans cells, B cells, and more - process and present antigen on their surface for recognition by antigen-specific B and T cells

Question 28

what % of your lymphocytes are circulating at any time?

Answer 28

10%

Question 29

how many lymph nodes do we have and how big are they?

Answer 29

500-600, size of a thumb or bean

Question 30

what must an antigen do to activate specific immune responses

Answer 30

the antigen must reach secondary lymphoid organs

Question 31

functions of the lymphatic system?

Answer 31

move antigen to secondary lymphoid organs to active specific immune responses and to take fluid from tissues and return it to the bloodstream

Question 32

two factors determining the response of the immune system to a foreign substance

Answer 32

nature of the substance and route of entry

Question 33

How does the immune system react to a bacterial infection under the skin to get the foeign antigen to a secondary lymphoid organ?

Answer 33

Specialised APC’s or dendritic cells (Langerhans cells - under the skin) take material from the microorganisms are the site of infection –> transport through lymphatics to nearest secondary lymphoid organ –> specific lymphocytes recognise and respond to the antigenic material