Antibodies

Question 1

What is the definition of antibodies?

Answer 1

Glycoproteins found in serum and tissues that are produced in large amounts after contact with immunogenic foreign molecules

Question 2

What part of immunity are antibodies involved in?

Answer 2

Humoural

Question 3

How many antibody classes are there? State them.

Answer 3

5 subclasses.
IgG, IgA, IgM, IgE, and IgD

Question 4

What is an alternate name for the Fab fragments combined?

Answer 4

Variable region

Question 5

Alternate name for Fc fragment/region

Answer 5

Constant region

Question 6

At what amino acid positions are the three hypervariable regions?

Answer 6

30, 50, and 90.

Question 7

What localised regions form the antigen binding site?

Answer 7

Framework regions and hypervariable sequences

Question 8

‘Antibody affinity’ refers to the interaction of:

Answer 8

A single antigenic determinant
Single Ab combining site
Product of the summation of forces

Question 9

3 main functions of the Fc region

Answer 9

Bind to Fc receptors on effector cells
Activate complement cascade
Regulate secretion so antibodies can widely distribute

Question 10

Complement cascade

Answer 10

Series of reactions that occurs on the surface of pathogens and generates active components with various effector functions

Question 11

Predominant Ab of primary immune response

Answer 11

IgM

Question 12

Affinity & avidity of IgM
+ why?

Answer 12

Low affinity because they are produced before B cells have undergone somatic hypermutation, but pentameric molecule so a large no. of binding sites and therefore high avidity

Question 13

Distribution of IgM

Answer 13

Limited to circulation due to large size

Question 14

First antibody produced and why

Answer 14

IgM because it can produces w/o class switching

Question 15

IgM heavy chain type

Answer 15

“mu”

Question 16

IgG heavy chain type

Answer 16

gamma

Question 17

Most abundant Ab in serum

Answer 17

IgG (70-75%)

Question 18

How many subclasses of IgG are there and how do they differ?

Answer 18

4 subclasses.
Differ in structure of the hinge region.

Question 19

IgG is:
a. Dimeric
b. A pentamer
c. Monomeric
d. A Hexamer

Answer 19

c. Monomeric

Question 20

Distribution of IgG

Answer 20

Extravascular (can cross into tissues easily)
Widespread distribution
Ig1, 3, and 4 can cross placenta for foetal immunity

Question 21

Opsonisation process

Answer 21

Fab binds to pathogen
Fc binds to phagocytic cells
Speeds up phagocytosis

Question 22

How many IgA subclasses are there?

Answer 22

2

Question 23

Type of heavy chain for IgA

Answer 23

alpha

Question 24

Where is IgA predominant?

Answer 24

Secretions like saliva and colostrum (first breast milk received by neonate)
Generally places w/o cells

Question 25

Secretory IgA is specialised for

Answer 25

Transport to areas w/o antibody-producing B cells

Question 26

How does IgA reach areas that don't have B cells?

Answer 26

When a B cell cannot pass it secretes dimeric IgA IgA uses secretory component polypeptide to bind to polymeric immunoglobulin receptor It can then be transported across to neutralise pathogenic toxins

Question 27

IgD heavy chain type

Answer 27

delta

Question 28

Signal transduction

Answer 28

Process by which a cell responds to substances outside the cell through signalling molecules on surface and inside the cell

Question 29

Function of IgD

Answer 29

Acts in signal transduction to stimulate B cell proliferation

Question 30

Where is IgD found?

Answer 30

The surface of circulating B lymphocytes

Question 31

Lowest serum level Ab

Answer 31

IgE

Question 32

What type (like genre) of cells does IgE interact with?

Answer 32

Granulocytes

Question 33

IgE and inflammation

Answer 33

Stimulates release of granules, which are pro-inflammatory agent by binding to Fc receptor on granulocytes. Associated w allergy.

Question 34

How do antibodies help fight infection? (4 things)

Answer 34

Antigen binding stimulates B cell activation Antibodies neutralise key receptors or pathogen products Block adhesion receptors Enhance Fc-mediated phagocytosis

Question 35

Antibodies and NK cells

Answer 35

Antibody binds to pathogen antigens Fc receptors on NK cells recognise bound antibody and cross-link -> sends signals Target cell dies by apoptosis

Question 36

Resting vs activated mast cells

Answer 36

Resting mast cell has granules that contain histamine and other inflammatory mediators Activated -> Multivalent antigen cross links bound IgE antibody, causing release of granule contents

Question 37

Base postulates of clonal selection hypothesis

Answer 37

Each lymphocyte bears a single type of receptor w unique specificity Binding w pathogen activates lymphocyte Differentiated effector cells from activated lymphocyte bear parental cell receptor Lymphocytes bearing receptors specific for ubiquitous self molecules are deleted at early stage of lymphoid development and are therefore absent from repertoire of mature lymphocytes

Question 38

Somatic recombination (Ab)

Answer 38

Rearrangement of genetic material that encodes Ab heavy or light chains Antigen-independent process that occurs in bone marrow

Question 39

Another name for somatic recombination is

Answer 39

V(D)J recombination

Question 40

How is rearrangement controlled?

Answer 40

Enzymes (recombinase activating genes expressed only during the process) DNA sequences (RSS)

Question 41

Junctional diversity

Answer 41

Cutting is imprecise when the segments are joined together, giving loss or gain of some nucleotides - P nucleotides

Question 42

N-region addition

Answer 42

template independent random addition catalysed by terminal deoxy transferase - heavy chain only

Question 43

RNA splicing

Answer 43

enables generation of IgM and IgD with specificity for same antigen