6 - Antigens and Antibody Structure - Partridge

Question 1

Draw a diagram to highlight the initial phases in response to infection

Answer 1

INNATE
INDUCED INNATE
ADAPTIVE

311 - 6 word

Question 2

Draw a diagram to highlight the OVERALL activation of the adaptive immunity in the draining lymph node

Answer 2

311 - 6 word

Question 3

Describe the organisation of the lymphoid tissue

Answer 3

Primary lymphoid tissue; lymphocytes reach maturity (B - bone marrow; T - thymus). Antigen INDEPENDENT differentiation -> naive t/B cells
Secondary lymphoid tissue; lymphocytes acquire their specific receptors. antigen DEPENDENT differentiation. eg in lymph nodes, spleen

Question 4

Antigens are recognised by ____ and ____ receptors on T/B lymphocytes

Answer 4

specific

diverse

Question 5

What occurs when appropriate receptors on B cells bind to antigen?

Answer 5

undergo clonal selection. B cells w/ correct receptor are stimulated to divide into plasma cells when bind to complementary antigen (which reach a point where they cannot divide further). plasma cells = Ab factories. some B cells retain their antigen receptor and persist as memory cells.

Question 6

What happens to lymphocytes that recognise self molecules?

Answer 6

detected early in development and degraded

Question 7

Do T cells undergo clonal selection?

Answer 7

yes, undergo clonal selection in response to antigen

Question 8

What are the 2 forms that Abs exist as?

Answer 8

• antigen recognition; integral membrane protein bound to B lymphocytes
• antigen elimination; soluble proteins secreted by plasma cells

Question 9

How does the structure of the antigen relate to its 2 functions in antigen recognition and elimination?

Answer 9

Fab arm; antigen recognition. specific sequences that recognise certain antigens, high sequence variability.
Fc region; antigen elimination. binds to Fc receptors on phagocytes, NK cells and complement to aid clearance of pathogen

Question 10

Draw the four chain structure of the IgG Ab

Answer 10

311 - 6 WORD

Question 11

Give the structure of IgG in terms of how many L and H chains there are and give the mw of these chains.

Answer 11

L2H2
L chain = 25kDa
H chain = 50kDa

Question 12

How can Abs be split up?

Answer 12

reducing followed by addition of an alkylating agent to stop the reformation of the disulfide bridges. in fact, more complicated than this because non covalent interactions also exist

Question 13

Draw a diagram to show the differential cleavage by papain and pepsin and the fragments that are created. Which one of the Fab fragments will more likely bind to antigen and why?

Answer 13

F(ab)2 more likely to bind. divalent therefore stronger interactions

311 - 6 word

Question 14

List the 5 main immunoglobulin classes and their functions

Answer 14

IgG - important in secondary responses. main class in serum and tissues
IgM - important in primary responses
IgA - secretions & secretions. protects mucosal surfaces
IgD -?
IgE - present in low amounts, parasites/allergy

Question 15

Name the 2 light chain types and state whether they are limited to one class.

Answer 15

k and lambda 
they are not class restricted eg IgGk or IgG(lambda). however Abs of the same type have the SAME light chain

Question 16

Protein sequencing on which proteins gave more information about Ab structure etc? Why was this protein used?

Answer 16

on myeloma proteins
myeloma = cancer cell in which B cells differentiates and divides uncontrollably therefore producing a large number of Abs. in blood we get large number of homogenous Abs.

Question 17

Describe the V region of Abs

Answer 17

variable region; differ between Abs of different specificities

Question 18

Describe the C region of Abs

Answer 18

same for a Abs of a given H chain class or L chain type

Question 19

Draw the structure of an Ab showing the different V/C regions

Answer 19

311 - 6

Question 20

Describe 1 homologous domain of an Ab ie anybonds, how many aa’s?

Answer 20

around 110 amino acids, intrachain S-S, folds into compact globular domain known as the immunoglobulin fold

Question 21

What do all members of the immunoglobulin gene superfamily contain and what type of receptors are they predominantly?

Answer 21

membrane-bound receptors. unlikely to be soluble proteins like Abs. all contain an immunoglobulin fold

Question 22

Why do some members of the Ig gene superfamily have v similar structures?

Answer 22

gene duplication events of Ig gene leading to a v similar folding pattern

Question 23

Why can’t we use x ray crystallography to solve the structure of the Ab as one and not as separate parts?

Answer 23

because the hinge region flexibility. means that many conformations will be seen.

Question 24

What is the hinge region of an Ab made up of?

Answer 24

extended proline chain

Question 25

Describe the structure of the L-chain C and V regions.

Answer 25

C region;
made up of 7 B strands, intrachain S-S
V region; made up of 9 B strands, intrachain S-S (more complicated region therefore more domain)

Question 26

how many members of the Ig gene superfamily are there in humans and what are they invovled in?

Answer 26

around 765 members

involved in binding, recognition and adhesion

Question 27

Draw the looped/B strand structure of the antigen combining site of the V region.

Answer 27

311 - 6

Question 28

give the name of the 2 main regions within the antigen combining site

Answer 28

framework region

hypervariable region

Question 29

What is the HVR also known as?

Answer 29

complementarity deterring region

Question 30

What are the type of interactions between the Ab and antigen?

Answer 30

non covalent interactions eg H bonds, electrostatic interactions, hydrophobic interactions, VDWs

Question 31

Describe the binding of the antigen combining site and antigen

Answer 31

individually weak interactions but if many interactions form at the same time then then become high affinity and specific. all relies on complementary residues between the antigen and ACS

Question 32

Overall, name the 3 results that were obtained through studying Ab structure of myeloma proteins.

Answer 32

1) Abs contain V and C regions
2) made up of homologous globular domains
3) the V region is made up of 3 hypervariable regions