Anti-bacterial responses

Question 1

What is the mechanism of S.aureus?

Answer 1

→Pore forming toxins
→Acute inflammation
→Superantigen

Question 2

What is the mechanism of V. choleare?

Answer 2

→Cholera toxin ADP ribosylation of G protein subunits – increase cAMP

Question 3

What is the mechanism of M. tuberculosis?

Answer 3

→Macrophage activation- granuloma and tissue destruction

Question 4

What is the mechanism Rickettsia?

Answer 4

→endothelial infection and dysfunction

Question 5

What is the mechanism of N. meningitidis?

Answer 5

→Acute inflammation,
→tissue damage
→sepsis due to potent endotoxin

Question 6

What are the main features of bacterial infection?

Answer 6

→bacterial pathogens live and replicate in extracellular spaces with exceptions
→most acute and dangerous bacterial diseases are caused not by the bacteria themselves but by the toxins they produce

Question 7

How many bacteria are there in the intestine?

Answer 7

→1014 essential bacteria

Question 8

What are the mechanical defences in the different parts of the body?

Answer 8

→flow of fluid
→perspiration
→urine
→mucus
→tears

Question 9

What are the chemical defences in different parts of the body?

Answer 9

→sebum(fatty acids, lactic acid, lysozyme)- skin
→enzymes(proteases)
→lysozyme in nasal secretion
→acidic vaginal secretion, spermine and zinc in semen
→lysozyme in tears

Question 10

What are the microbiological defences in the body?

Answer 10

→normal flora

Question 11

What are defensins?

Answer 11

→Anti-microbial peptides capable of killing by penetrating microbial membranes thus disrupting their integrity

→active against bacteria, fungi and many enveloped and non-enveloped viruses

Question 12

What are the types of defensins?

Answer 12

→𝛂-defensins

→β-defensins

Question 13

What are alpha-defensins secreted by?

Answer 13

→mainly by neutrophils

→Paneth cells

Question 14

What are Paneth cells?

Answer 14

→highly specialized secretory epithelial cells located in the small intestinal crypts of Lieberkühn

Question 15

What are beta-defensins secreted by?

Answer 15

→broad range of epithelial cells

→in the respiratory tract, the skin and the urogenital tract

Question 16

Describe the classical complement pathway

Answer 16

→triggered by antibody-antigen complexes binding to C1
→forms a C3 convertase
→C4b2a, which splits C3 into two fragments; the large fragment, C3b, can covalently attach to the surface of microbial pathogens
→opsonise them
→C3a, activates mast cells, causing the release of vasoactive mediators such as histamine

Question 17

Describe the alternative pathway

Answer 17

→factors, B, D, H & I, interact with each other, and with C3b, to form a C3 convertase

→activates more C3

Question 18

Describe the lectin pathway

Answer 18

→mannose-binding lectin (MBL) to mannose residues on the pathogen surface
→activates the MBL-associated serine proteases
→activate C4 and C2, to form the C3 convertase, C4b2a

Question 19

What are the outcomes of C3 and C5 convertases?

Answer 19

→inflammation- recruitment of C5a and C3a
→lysis- C3b bind to bacteria
→opsonisation

Question 20

Describe the structure of TLRs

Answer 20

→leucine-rich repeat motifs

→cysteine-rich flanking motif

Question 21

Which type bacteria is TLR4 found on?

Answer 21

→gram negative, LPS

Question 22

Which type of bacteria is TLR2 found on?

Answer 22

→gram positive, peptidoglycan

Question 23

Which types of complement molecules are involved in mast cell degranulation?

Answer 23

→C3a

→C5a

Question 24

What 3 cells are involved in inflammation?

Answer 24

→monocyte via VCAM on blood vessel
→neutrophil via P-selectin
→lymphocyte via ICAM

Question 25

How else can neutrophils kill bacteria?

Answer 25

→Neutrophils Extracellular Traps (NETS)

Question 26

What are the three functions of Abs?

Answer 26

→Neutralise bacterial toxins
→Trigger classical complement pathway by binding of IgM to the bacterial cell surface
→Opsonisation; coating of bacteria with antibody thereby aiding phagocytosis

Question 27

What does IgM targeting of bacteria initiate?

Answer 27

→classical pathway of complement

→bacterial cell surface is coated in C3b facilitating its phagocytosis

Question 28

Which Ab is most active in neutralisation?

Answer 28

→IgG

→IgA

Question 29

Which Ab is most active in opsonisation?

Answer 29

→IgG

Question 30

Which Ab is most in NK killing?

Answer 30

→IgG

Question 31

Which Ab is most in mast cell sensitisation?

Answer 31

→IgE

Question 32

Which Abs are most active in activation of complement?

Answer 32

→IgM

→IgG

Question 33

Which Ab can cross the epithelium?

Answer 33

→IgA

Question 34

Which Ab can cross the placenta?

Answer 34

→IgG

Question 35

Which Ab can diffuse into extravascular spaces?

Answer 35

→IgG

→IgA

Question 36

Where do dendritic cells present to T-antigen cells?

Answer 36

→secondary lymphoid organs

Question 37

Example of pathogen that can survive inside macrophages

Answer 37

→Micobacterium tuberculosis

Question 38

Which cytokine can activate NK cells?

Answer 38

→IL-12

→produced from macrophages