Intro to immunology

Question 1

What are the major physical barriers to infection?

Answer 1

Saliva
Mucocilliary Escalator
Gastric Acid
Natural Flora
Flushing & urine pH

Question 2

What cell types are involved in innate immunity?

Answer 2

In blood:

• NK cells
• Basophils
• Eosinophils
• Monocytes

In Tissue

• Mast Cells
• Macrophages
• Dendritic Cells

Question 3

By what mechanisms does the innate immune system function?

Answer 3

1) Inflammation
2) Recruiting immune cells
3) Complement Activation
4) Opsonisation
5) Phagocytosis
6) NK cytotoxicity

Question 4

What are cytokines?

Answer 4

Molecules that regulate the nature, duration & intensity of immune responses by binding to specific receptors
E.g. Interleukins, TNF-alpha, chemokines & TGF-beta

Question 5

Where are cytokines made?

Answer 5

Th cells & Macrophages

Question 6

Which cytokines are pro and anti-inflammatory?

Answer 6

Pro-inflammatory = TNF-alpha, IL-1, IL-6 & chemokines

Anti-inflammatory = IL-10 & TGF-beta

Question 7

Describe what happens during inflammation?

Answer 7

Pattern Recognition Receptors (PRR) detect a breach in defence/foreign body and trigger:

• Vasodilation
• Vascular permeability
• Cell Adhesion Molecules
• Chemotaxis
• Sensitivity to Pain

Question 8

How is complement activated?

Answer 8

C3 is activated first. By any of the 3 pathways, Classical/Lectin/Alternative

Question 9

What are the functions of complement?

Answer 9

Chemotaxis of phagocytes
Opsonisation
Lysis of micro-organisms
Maintain solubility of Ab/Ag complexes

Question 10

What is Opsonisation?

Answer 10

Tagging cells for phagocytosis

Done by complement C3b/C4b, antibodies & plasma cells

Question 11

What do NK cells do in innate immunity?

Answer 11

Perforin-induced Apoptosis

Question 12

Define an antigen vs antibody?

Answer 12

Antigen is any molecule that induces an immune response. An antibody is a glycoprotein made by b cells that binds antigens

Question 13

What are the 2 types of adaptive immunity?

Answer 13

Humoral - B cells & Abs

Cell-mediated - T Lymphocytes

Question 14

How do adaptive immune cells recognise antigens?

Answer 14

B cells/Abs detect BCR directly

T cells detect MHC on antigen presenting cells

Question 15

Immune Tolerance is a process of ensuring our Lymphocytes are tolerant towards our own tissues. Where does this occur?

Answer 15

Central Tolerance:
T = Thymus
B = Marrow

Peripheral Tolerance:
- 2nd lymphoid organs & circ

Question 16

What happens during central tolerance?

Answer 16

B cells assessed for self-reacting BCR in the marrow.

T cells undergo +ve (can they recognise foreign antigen?) & -ve (Do they not recognise self-antigens) tolerance testing in the thymus.
Any failures die

Question 17

How does peripheral tolerance work?

Answer 17

Regulatory T cells destroy self-reactive lymphocytes

Question 18

What are the major types of T cells?

Answer 18

Cytotoxic (CD8+)
Helper (CD4+)
Regulatory

Question 19

What do CD8+ T cells do?

Answer 19

Cytotoxic

They induce apoptosis in target cells and release anti-viral/tumour cytokines (IFN-gamma & TNF-alpha)

Question 20

What do CD4+ T cells do?

Answer 20

Helper:
Activate B cells

Also release cytokines and activate other inflammatory cells e.g. macrophages, mast cells, basophils etc.

Question 21

Which type of Th cell attacks which type of pathogen?

Answer 21

Th1 targets intracellular pathogens

Th2 & Th17 target extracellular pathogens

Question 22

Other than peripheral tolerance, what else do regulatory T cells do?

Answer 22

Secrete anti-inflammatory Cytokines (IL-10 & TGF-beta)

Suppress Th & cytotoxic T cells

Question 23

Which immunoglobulins are monomers, dimers & pentamers?

Answer 23

Monomer - IgG, IgE, IgD

Dimer = IgA

Pentamer = IgM

Question 24

Which immunoglobulin can cross placenta?

Answer 24

IgG

Question 25

Which immunoglobulin is involved in parasites and allergies?

Answer 25

IgE

Question 26

Which antibody activates complement?

Answer 26

IgM

Question 27

What are the functions of immunoglobulins?

Answer 27

1) Immune complex formation
2) Opsonisation
3) Classical Complement Activation
4) Ab-dependant Cellular Cytotoxicity (ADCC)

Question 28

What are the major causes of Secondary Immune Deficiency?

Answer 28

Environmental e.g. malnutrition or trauma

Disease e.g. HIV, DM, malignancy or renal failure

Drugs e.g. Glucocorticoids, cyclosporin or Rituximab