Immunoglobulins

Question 1

Are antibodies proteins?

Answer 1

Yes

Question 2

What are the aspects to antibodies?

Answer 2

• 4 polypeptide chains (2 light chains and 2 heavy chains)
• 4 chains held together by disulfide bonds

Question 3

What is a ligand?

Answer 3

Any molecule that binds to a protein

Question 4

What is an antigen?

Answer 4

Any molecule that is recognized and bound by an antibody (has components of the adaptive immune system)

Question 5

What is an epitope?

Answer 5

The specific part of an antigen recognized by an antibody

Question 6

What is another name for immunoglobulins

Answer 6

Antibodies

Question 7

What is a bivalent antibody?

Answer 7

When 1 antibody binds to 2 of the same antigens (a monomer that contains 2 antigen binding sites)

Question 8

What is a constant region?

Answer 8

AA sequence that doesnt very, very much (compared to other regions of the antibody)

Question 9

What is a variable region?

Answer 9

Differ in AA sequence from one immunoglobulin to the other

Question 10

Where do antibodies bind to their targets (= antigen)

Answer 10

Variable region

Question 11

What type of protein structure do immunoglobulins have?

Answer 11

Tertiary

Question 12

What type of lymphocytes make antibodies?

Answer 12

B-lymphocytes

Question 13

What is a hypervariable region?

Answer 13

A region where there is greater AA sequence diversity and the area where epitopes bind to the tips of the antibodies

Question 14

What occurs when an antibody is treated with papain?

Answer 14

Causes a cleave in the hinge region which leads to the release of 2 arms (these are called fab fragments and contain antigen binding sites)

Question 15

What are the 2 functions of the FC region?

Answer 15

• Potentially anchor membranes in the plasma membrane
• Mediates downstream effector functions that come in to destroy pathogens

Question 16

What is the hinge region on an immunoglobulin?

Answer 16

Area that provides flexibility to the molecule and allows the molecule to change shape, which is helpful in binding to antigens of different shapes and sizes

Question 17

Where do epitopes bind?

Answer 17

To the tips of antibodies at their hypervariable sequences

Question 18

How many heavy chain permutations?

Answer 18

5520 (40 V, 23 D, 6J)

Question 19

How many light chain permutations?

Answer 19

295 (2 loci: 175 kappa + 120 lambda)

Question 20

Overall purpose of B-lymphocyte development

Answer 20

Going from membrane bound to secreted

Question 21

B-lymphocyte development

Answer 21

• Lymphoid progenitor cells
  — Proliferation and B cell diversification in bone marrow
• Different resting B cells
  — About 10^12 sequence variants
• Antigen binds
  — Proliferation and differentiation of B-Beta cells
• Antibody secreting B-Beta cells
• Secreted antibodies (they can seek out the antigen)

Question 22

IgM

Answer 22

Membrane bound (initial antibodies from immature B cells)

Question 23

IgG

Answer 23

Class of antibodies that actually gets secreted and released from cells

Question 24

In antibody trafficking, where are proteins directed?

Answer 24

They are directed to the secretory pathway by a signal at their amino terminus

Question 25

Antibody trafficking order

Answer 25

ER -> Golgi App -> Plasma Mem (fusion)

Question 26

Antibody trafficking default pathway

Answer 26

• Proteins in the lumen of the ER are secreted from cells
  *Proteins with signals that anchor them in the ER membrane can end up at the plasma membrane

Question 27

What do plasma membrane protein’s (IgM) consist of?

Answer 27

Signal peptide + stop transfer

Question 28

Where is an IgM’s heavy chain stop transfer sequence?

Answer 28

Within its FC domain

Question 29

During B-cell maturation, why is a switch made from IgM to IgG?

Answer 29

Because IgG heavy chain LACK a stop transfer codon
*The switch is in the last cassette (CR) from Mu to Gamma
**Occurs so that secretion can occur (stop transfer sequence is removed)

Question 30

IgA

Answer 30

IgA’s have a protective function when they are secreted into the saliva

Question 31

Are IgA’s found in blood

Answer 31

NO

Question 32

Where are IgA’s produced?

Answer 32

Connective tissue of a specialized plasma cell that is polarized and below epithelial cells

Question 33

Do IgA’s form dimers?

Answer 33

YES

Question 34

How are plasma cells and B-cells related?

Answer 34

Plasma cells ARE mature antibody-producing B cells

Question 35

What recognizes IgA dimers?

Answer 35

plgR’s recognize IgA dimers and fuse with the apical surface and release the IgA’s into the saliva

Question 36

What are super secondary structures?

Answer 36

Groupings of secondary structure elements

Question 37

What are immunoglobulin folds?

Answer 37

Domains of super-secondary structures that hold chains together non-covalently and are repeated

Question 38

What is Rituximab?

Answer 38

First clinically used monoclonal antibody

Question 39

4 properties of an ideal tumor associated antigen (TAA)

Answer 39

• Expression on all tumor cells
• Expression on tumor cell surface
• Functions in tumor cell survival
• Lack of expression on normal tissues
  *No current TAA’s display ALL of these ideals

Question 40

What is a good target for a therapeutic antibody to treat B cell hyper-proliferative disorders?

Answer 40

CD20

Question 41

What does Rituximab recognize?

Answer 41

Recognizes CD20 antigen (CD’s are names for bio markers in different cell types)

Question 42

Do early progenitors express CD20?

Answer 42

NO (b-cell adaptive immunity can be restored after)

Question 43

What interactions do super secondary structures drive?

Answer 43

Protein-protein interactions

Question 44

What is the structure of super secondary structures?

Answer 44

4-stranded antiparallel beta sheet overlaying a 3-stranded antiparallel beta sheet

Question 45

Types of tumor cell death

Answer 45

• Complement mediated lysis
• Phagocytosis
• Block protein function and kill tumor directlyy