Recognition of extracellular pathogens

Question 1

What is an antigen

Answer 1

Any part of a pathogen that is recognised by the immune system

Question 2

What is the epitope

Answer 2

The region of the antigen that binds to the antibody binding site

Question 3

Clonal selection

Answer 3

Competition between B cells for interaction with the antigen
B cell with the most complementary antigen binding site to antigen
This B cell now proliferates
Most of these cloned B cells become plasma cells ; some become memory cells

Question 4

Immunoglobulin structure

Answer 4

4 polypeptide chains ; 2 heavy , 2 light
2 identical antigen binding site formed by the terminal regions of where the heavy and light chains overlap
Globular regions forming domains ; 4 in heavy chains , 2 in light chains
Disulphide bonds join the heavy and light chains

Question 5

Name the isotopes of immunoglobulins

Answer 5

IgA
IgM
IgE
IgD

Question 6

Label the Fab and Fc regions on the antibody

Answer 6

Question 7

What is the purpose of different immunoglobulin isotopes?

Answer 7

Constant region of antibody can interact with other components of the immune system ; different isotopes lead to different responses

Question 8

Identify which antibody isotope is responsible for each interaction with a defence component :

1) Complement activation
2) Phagocyte binding
3) Mast cell binding
4) NK cell binding

Answer 8

1) IgM, IgG
2) IgG, IgA
3) IgE
4) IgG

Question 9

What is a complement protein?

Answer 9

Collection of proteins found in circulation and tissue fluids that complements the effects of antibodies

Central event in complement activation is the splitting of them by enzymes

Normally remain inactive

Question 10

Macrophages

Answer 10

Posses innate microbe receptors such as FcR and CR

Question 11

Function of opsonins

Answer 11

Proteins that bind to microbe that attract macrophages to bind

Question 12

Function of acute phase proteins

Answer 12

Produced by liver during infection ;
Serum amyloid protein (
C-reactive protein/Mannan binding lectin (act as opsonin and complement activator)
Fibrinogen

Question 13

Describe the action of eosinophils

Answer 13

Complement protein/antibody receptors on surface of eosinophil allow its attachment to parasite

Releases digestive enzymes onto surface of parasite ( extracellular digestion)

Question 14

What is the role of mast cells and how are they activated?

Answer 14

Found in tissues throughout body 
Similar to basophils 
Release inflammatory mediators such as histamine(immediate release) and prostaglandins 
Activated by action of IgE antibodies
Can also be activated by C3a and C5a

Question 15

Which cells release prostaglandins ?

Answer 15

Macrophages and mast cells

Question 16

Which cells release cytokines ?

Answer 16

Macrophages and T cells

Question 17

Which inflammatory mediators are responsible for leukocyte adhesion?

Answer 17

Selectins and integrins

Question 18

Which inflammatory mediators are responsible for chemotaxis of leukocytes?

Answer 18

Chemokines

Question 19

Describe the key features of the systemic (whole body) inflammatory response

Also identify the inducing cytokines

Answer 19

Inducing cytokines : IL-1 , IL-6, TNF

Key features
Fever
Leucocytosis - particularly neutrophils ; from bone marrow
Acute phase proteins from liver - CRP