Lecture 20-21: Immunoglobulin

Question 1

What are the two regions of an immunoglobulin

Answer 1

• variable region

- constant region

Question 2

What functions does the variable region do?

Answer 2

• mediate antigen bonding

- differ between immunoglobulins

Question 3

What functions does the constant region do?

Answer 3

• effector functions

- conserved between immunoglobulin of one isotype

Question 4

What is the structure of immunoglobulins

Answer 4

• 4 polypeptide chains, 2 light and 2 heavy

- held together by disulphides linkages

Question 5

What two things can digest immunoglobulins

Answer 5

• papain

- pepsin

Question 6

What does papain do

Answer 6

• breaks it into three parts
• Fab which can bind the antigen
• Fc which is crystallized
• unable to precipitate antigen

Question 7

What does pepsin do?

Answer 7

• F(ab’)2 binds and crosslinks antigen
• Fc fragment is not recovered
• able to precipitate antigen

Question 8

What are complementarity determining regions

Answer 8

Regions that form loops and bind to the antigen

Question 9

What are framework regions

Answer 9

Remaining variable domain regions

Question 10

What do CL and CHL do?

Answer 10

• add flexibility to antigen binding

- stabilize H-L chain interactions

Question 11

What is CH(2-4)?

Answer 11

-hydrophilic

Question 12

What are idiotypes

Answer 12

Collections of antigenic determinants in the variable region

Question 13

What is a idiotope

Answer 13

Each individual determinant is known as an idiotope

Question 14

What are Ig alpha and Ig beta

Answer 14

Ig binds with them and it helps generate signals through immunoreceptor tyrosine-based activation motifs

Question 15

What can an Ig bound to an Ag activate in a pathway?

Answer 15

Complement, must bind to two at the same time

Question 16

How do antibodies neutralize

Answer 16

It coats a target in antibodies prevents them from adhering to cells

Question 17

Explain Fc receptors

Answer 17

Ig bound to bacteria is able to cross link Fc receptors which generated a signal

Question 18

What can binding of Fc receptors do

Answer 18

• phagocytosis (opsonization)
• Ab dependent cell mediated cytotoxicity
• granulocyte degranulation

Question 19

What is Ab dependent cell mediated cytotoxicity

Answer 19

Binding of NK cell to Fc starts a release of cytotoxic stuff that kills a target

Question 20

What is granulocyte degranulation

Answer 20

Cross linking of the Fc bound IgE by an antigen induces degranulation

Question 21

What is the lifespan facts of a B cell

Answer 21

• continuously produced throughout life
• short half life’s of 3-4 days
• they must encounter an antigen to survive

Question 22

Where are B cells produced and where do they hang out

Answer 22

Bone marrow and lymph node

Question 23

What is hypermutation

Answer 23

Process by which B cells are mutated to bind with antigens

Question 24

In germinal centres what are the two zones

Answer 24

The dark zone which is dividing centroblasts and light zone which is selection and maturation of centrifuged

Question 25

What B cells are picked for survival

Answer 25

Centrocytes with high affinity receptors are selected for survival and will die unless they bind to antigens