4 Antibodies - specificity and function

Question 1

antigen origin name

Answer 1

from antibody generator

Question 2

epitope

Answer 2

Many antibodies may bind the same antigen, each a separate site termed an antigenic determinant or epitope – antibodies recognise epitopes

Question 3

what epitopes do antigens show

Answer 3

can also show repeated epitopes

Question 4

what structure are antigens

Answer 4

can be diverse molecular structures

Question 5

two effector cell types

Answer 5

B lymphocytes

T lymphocytes

Question 6

B lymphocytes (B cells)

Answer 6

• make antibodies (immunoglobulins) - cell surface and secreted
• can improve the antibodies made over time
• protection against extracellular pathogens & toxins

Question 7

T lymphocytes (T cells)

Answer 7

• express T cell receptors (TCR)
• interact with other cells
• can kill cells, or facilitate immune responses by other cells
• Killer T cells (CD8+), Helper T cells and regulatory T cells (CD4+)

Question 8

variable region

Answer 8

antigen-binding site

Question 9

constant region

Answer 9

binds to cellular receptors – effector function

heavy chains have a hinge region in middle that gives a flexibility to the antibody

Question 10

adaptive immune system

Answer 10

It changes over time!

Question 11

immunoglobins examples

Answer 11

Serum glycoproteins also found in tissue fluids
B lymphocytes
antibodies

Question 12

B lymphocytes

Answer 12

> surface antigen receptor (B cell receptor; BCR)

> associates with other cell surface proteins

Question 13

Plasma cells produce

Answer 13

secretory immunoglobulin (antibody)

Question 14

antibody classes

Answer 14

five classes of antibody: IgG, IgA, IgM, IgD & IgE

Question 15

what is the first antibody line of defence

Answer 15

IgM

Question 16

bonds in antiobodies

Answer 16

disulphide

Question 17

what enzymes can be used in enzymatic cleavage

Answer 17

papain

pepsin

Question 18

what happens if us papain enzyme for cleavage

Answer 18

• 2x Fab, (Fragment- antigen binding)

- Fc (Fragment-crystallizable)

Question 19

what happens if use pepsin enzyme for cleavage

Answer 19

• Fab(2), bivalent binding

- Fc fragments

Question 20

why is an antibody bifunctional

Answer 20

• antigen binding

- ability to trigger effector functions

Question 21

what light chains could be in a B cell

Answer 21

any one b cell will only use either kappa or lambda chain

Question 22

constant region of a light chain

Answer 22

CL

Question 23

variable region of a light chain

Answer 23

VL

Question 24

variable domain of a heavy chain

Answer 24

CH1, CH2, CH3, sometimes CH4

Question 25

constant domain of a heavy chain

Answer 25

VH

Question 26

antibody flexibility

Answer 26

Hinge regions | hinge of IgG subclasses is what makes them differ

Question 27

Serum concentrations and half-life of IgG1

Answer 27

High concentration for IgG1 in serum | Half-life varies in subtypes – IgG1 usually longest

Question 28

Serum concentrations and half-life of IgG3

Answer 28

IgG3 not found in serum is found in the skin = low concentration in serum

Question 29

what makes up the domain structure of antibodies

Answer 29

- Variable (V) | - Constant (C)

Question 30

what is the complementarity determining region

Answer 30

``` Peptide loops (hypervariable regions) are involved in interactions with antigen Hypervariable regions (loops) interact with antigen ```

Question 31

how many complementarity determining regions does the heavy and light chains have each

Answer 31

3 CDRs each

Question 32

what forms a paratope

Answer 32

Combination of H+L CDRs produces the unique antibody combining site

Question 33

where is a paratope

Answer 33

within the antibody

Question 34

what holds the antigen into place

Answer 34

non-covalent interactions of the paratope with the antigenic epitope

Question 35

Size of antigens and area of interaction varies

Answer 35

Small, can fit into the antibody Lay across the antibody Globular, antibody can open up slightly and sit on it

Question 36

Conformational specificity of an antibody

Answer 36

an antibody may recognise a specific 3D conformation of protein

Question 37

primary sequence recognised by antibodies

Answer 37

linear epitope

Question 38

secondary sequence recognised by antibodies

Answer 38

constrained secondary structure epitope (e.g. a loop or turn)

Question 39

tertiary structure recognised by antibodies

Answer 39

discontinuous epitope (tertiary structure epitope) Tertiary structure gives the epitope

Question 40

affinity

Answer 40

strength of a single antibody (Fab)/antigen bond

Question 41

avidity

Answer 41

- Binding of a multivalent antibody to a multivalent antigen | - Avidity is likely to be the physiologically relevant affinity (functional affinity)

Question 42

effect of bivalent antibody

Answer 42

equilibrium constant higher, functional ability increased as avidity higher

Question 43

Fab binding

Answer 43

affinity

Question 44

IgG bindings

Answer 44

affinity or functional avidity

Question 45

IgM binding

Answer 45

affinity and avidity

Question 46

how do antibody isotopes differ

Answer 46

hinge regions

Question 47

IgM antibody structure

Answer 47

form a pentameric structure – using a joining chain protein and disulphide bonds – how circulates in body

Question 48

why has IgM got a higher molecular weight

Answer 48

circulating as a pentamer

Question 49

IgA antibody structure

Answer 49

dimer in the body

Question 50

isotope physical differences

Answer 50

- CH1-CH2 hinge length - Interchain disulphide bond location and number - Number of CH domains - Variable glycosylation - Multimer capability

Question 51

what is a multimeric immunoglobin

Answer 51

When antibodies come together some can become relatively large

Question 52

Tissue distribution of IgG isotopes

Answer 52

IgG in most places

Question 53

Tissue distribution of IgM isotopes

Answer 53

IgM when secreted mainly in peripheral blood

Question 54

Tissue distribution of IgA isotopes

Answer 54

Dimeric IgA in mucosa – upper respiratory tract and gut

Question 55

Tissue distribution of IgE isotopes

Answer 55

IgE mainly in skin, as allergic reactions take place here e.g. basophils and mast cells

Question 56

Tissue distribution of IgD isotopes

Answer 56

IgD expressed in upper respiratory tract, possibly more important than IgA

Question 57

Effects of pathogen specific antibodies

Answer 57

- Neutralize toxins - Block virus binding and entering cells - Opsonise pathogens - Activate complement

Question 58

where are Antibody receptors present

Answer 58

Fc receptors present on phagocytic cells

Question 59

Antibody function

Answer 59

Different classes have different functions

Question 60

antibody capabilities

Answer 60

> Neutralisation > Complement activation > Opsonization cytotoxicity

Question 61

what occurs at IgG

Answer 61

location of effector function sites