AntibacteriL Responses

Question 1

What are some examples of pathogenic bacteria?

Answer 1

S aureus - skin and soft tissue, lungs,toxic shock

V. Choleara - Diorrhea

M. Tuberculosis - TB

N meningitids. - meningitis

Question 2

What are the features of a bacterial infection?

Answer 2

Live and replicate in extracellular spaces with exceptions

Most acute and dangerous disease are caused by toxins not bacteria themselves

Infection is an interaction between the pathogen and the host

Question 3

What are some general features of immunity to bacteria?

Answer 3

Innate and adaptive immune system involved

Pathogenic it an survival of the bacteria is critically influenced by the ability to evade the effector mechanism of immunity

Some bacteria are latent or persistent infection - immune system does not clear the microbe

Tissue damage is most associated with immunity then infection

Question 4

What are the 3 different innate immune responses?

Answer 4

Mechanical

Chemical

Microbiological

Question 5

What are anti bacterial peptides (defensins)?

Answer 5

capable of killing by penetrating microbial membranes thus distrusting their integrity

Active against bacteria, fungi and non enveloped viruses

Question 6

What are the two types of defensins?

Answer 6

Alpha and beta

Alpha - secreted mainly by neutrophils and by paneth cells

Beta - secreted by broad range of epithelial cells, skin and. Urogenital tract

Question 7

What is the complement?

Answer 7

A key effector function of the humoral response

A pathogen recognition receptor and serum that interact with each other to generate products that eliminate extracellular bacteria

Activated when bacteria cross the barriers by microbial cell wall

Question 8

What is the function of the complement?

Answer 8

Tags microbe through opsonisation so that phagocyte can recognise tag and phagocytosis can take place

Tags microbe to help recruit and activate leukocytes to stimulate inflammation

Complement mediated cytolysis - form a membrane attack complex o the bacteria leading t osmotic lysis

Question 9

What complement receptors are expressed on phagocytes?

Answer 9

CR3

CR1

CR4

Question 10

What are TLR Pathogen recognition receptors?

Answer 10

Toll-like receptors

Intracellular - TLR 3,7,8,9

On cell surface - TLR 4,5,2,1

Question 11

Whats the difference in TLRs in gran negative and positive bacteria?

Answer 11

Posative bacteria - peptidoglycan by TLR2

Negative bacteria - LPS by TLR4

Question 12

What are the roes of neutrophils and bacteria infection?

Answer 12

Phagocytosis and degranulation off granules intracellular killing of bacteria

Can kill bacteria phagocytsing bacteria - Neutrophils extraccellulaar traps (NETS).

Question 13

What is function of the antibodies?

Answer 13

Neutralise bacterial toxins

Trigger classical complement pathway by binding of igM to the bacterial cell surface

Opsonisation - coating bacterial body an idling with phagocytosis

Question 14

What occurs during toxin neutralisation?

Answer 14

1. Toxin binds to cellular FC receptors
2. Endocytosis of toxin-receptor compexes
3. Dissociation of toxin to release active chain,, which poisons cell
4. Antibody protects cell by blocking binding of toxins to FC receptors on cells

Question 15

Describe what occurs when triggering the complement cascade

Answer 15

1. Pentamric igM molecules bind to antigen on the bacterial surfacce and adopt a “stable” form
2. C1q binds to one bound igM molecule
3. This activates C1 Which cleaves and activates serine proteases C1

Question 16

Describe how helper T cell enhance phagocytosis

Answer 16

Macrophage engulfs and degrades bacterium producing peptides

Bacteria peptides bound by MHC class 2 in vesicles

Bound peptides transported by MHC class 2 to the cell surface

Healer T cell recognises complex of peptide antigen with MHC 2 and activates macrophage