Immune Response To Infection

Question 1

What type of pathogen niches are there during infection?

Answer 1

Extracellular
Intracellular
Surface adherent
Intracellular but cytosolic

Question 2

How does an immune infection start?

Answer 2

Tissue damage
Molecular detection of pathogens
Intercellular communication (e.g. interleukins)
Priming adaptive immune response

Question 3

How does an immune response to an infection end?

Answer 3

Cleaning infection
Stopping inflammatory cytokine production
Repairing tissue damage
Immune memory

Question 4

What are properties of the innate immunity?

Answer 4

Fast acting, first line of defence, germline encoded receptors

Physical barriers: skin, mucous, epithelial cells

Humoral response: complement, lectins, pentraxins, antimicrobial peptides

Cellular response: Neutrophils, macrophages, DCs, NK cells

Question 5

What are properties of the adaptive immunity?

Answer 5

Slower, long term, variable receptors that mature overtime (somatic hypermutation)

Humoral response: antibodies, complement

Cellular response: Cytotoxic T cells, T helper cells, Treg cells, B cells, Plasma cells

Question 6

What are the first responders to a pathogen?

Answer 6

Neutrophils and macrophages

Neutrophil response is short lived then followed by macrophage response

Question 7

What happens when naive cells interact with pathogens?

Answer 7

Naive cells become activated

Phagocytes control infections and limit tissue damage

Question 8

What can uncontrolled activation of phagocytes lead to?

Answer 8

Granulomas
Excessive inflammation and inappropriate adaptive immunity
Tissue damage

Question 9

How do phagocytes respond to bacteria?

Answer 9

Immune response includes:

• inflammatory cytokines
• antimicrobial genes
• metabollic genes
• immunomodulatory genes

Question 10

How do phagocytes respond to fungi?

Answer 10

Proinflammtory cytokines
Metabollic genes
Immunoregulatory genes

Question 11

How do phagocytes respond to viruses?

Answer 11

Interferon production
Proinflammtory cytokines
Antiviral genes
Immunregulatory genes

Question 12

What does macrophage activation cause?

Answer 12

Macrophage activation = expression of new genes
Activation is induced by microbes or cytokines

Activated macrophages display enhanced:

• phagocytosis and migration
• cytokine/chemokine production
• expression of cell surface molecules
• antimicrobial activity
• antigen presentation and T cell activation

Question 13

How do phagocytes kill pathogens?

Answer 13

1. Macrophage is infected
2. Macrophage releases set of cytokines: IL-12, IL-18, IL-1, TNF, IL-6
3. These cytokines are detected by T cells causing them to produce cytokines e.g. type II interferon (IFN gamma)
4. Cytokines (e.g. IFN- gamma) acts on macrophages and produces new genes that are directly toxic to microbes
5. Macrophage become activated and kills the phagocytosed microbe

Question 14

How do interferons promote antiviral defence?

Answer 14

Interferons are special cytokines
They direct antiviral activities
Antiviral genes include:
-nucleases
-inhibitors of viral entry and exit
-inhibitors of protein translation
-inhibitors of viral uncoating and replication

Question 15

How are infected cells killed?

Answer 15

Infected cells are killed by cytotoxic T lymphocytes (CTL) or NK cells

Question 16

What are examples of humeral innate immunity?

Answer 16

Phagocyte Oxidase- produces large amount of reactive oxygen species

Inducible nitric oxide synthase (INOS) is a radical that is highly toxic to intracellular pathogens

These genes are only present in an activated cell

Question 17

What are humoral soluble effector mechanisms?

Answer 17

Compliment mediates bacterial destruction

Lectin binding to neutralise cell attachment or entry

Iron chelation (siderophores) to prevent replication

Antibiotic like peptides

Question 18

What are humoral cellular effector mechanisms?

Answer 18

Reactive oxygen and nitrogen radicals

Acidification and digestion with phagosomes

Question 19

How do dendritic calls and macrophages activate T cells?

Answer 19

Activated macrophages and DC’s present antigens in combination with MHC-I and MHC-II to T cells
Cytokines produced by antigen-presenting cells causes activation of T cells
T cells provide cytokines that activate phagocytes

Question 20

How do T cells and B cells enhance antimicrobial immunity?

Answer 20

Phagocyte activation: enhances killing of pathogen and inflammation

Direct killing of infected cells

B cell activation: antibody production

Question 21

How does age impact immune response?

Answer 21

Weaker immune response with older age
Decreased thymus output so less T cells made
Memory T cells keep increasing however because you encounter many different infections over years