Lecture 6:Antibodies

Question 1

Immunoglobulins are

Answer 1

Immunoglobulins are also called antibodies
Part of the humoral immune system

Question 2

Antibodies are produced by

Answer 2

Produced by plasma cells
Derived from B cells.
Different types with different purposes

Question 3

Importance of antibodies

Answer 3

Host defense (binding and neutralization)
Vaccination
Testing

Question 4

Antibodies are used for diagnostics how

Answer 4

Used diagnostically to detect infections
Rising titers
Means higher serum antibody levels.
Recent infection

Question 5

Antibodies are used for

Answer 5

Used to fight infections.
Vaccines boost antibody titers – often the basis for judging their effectiveness.
Hyperimmune sera may be prescribed to treat infections

Question 6

Basic immunoglobin structure

Answer 6

All immunoglobulin molecules have the same basic flexible Y shape with a hinge region.
The stalk/tail of Y is the crystallizable fragment (Fc)
Top of Y is two antigen binding fragments (Fab)

Question 7

The stalk of immunoglobulin does

Answer 7

Constant within an antibody class
Determines class of immunoglobulin
Responsible for effects of the Ig when the head binds an antigen.

Question 8

Top of the Y in immunoglobulin is

Answer 8

Composed of both constant and variable regions
A given clone of plasma cells (daughters of a common B cell) produce an Ig that is specific for one particular antigen

Question 9

Fc mediates binding to

Answer 9

Host tissue
Various cells of the immune system
First component of complement system

Question 10

Fab binds antigen for

Answer 10

Marks antigen for immunological attack
Activates nonspecific defense mechanisms that can destroy antigen
e.g., opsonization for enhanced phagocytosis

Question 11

Site of production of immunoglobulin

Answer 11

Ig are produced by B Cells and Plasma Cells
B cells put Ig on their surface
Plasma cells excrete Ig into the body fluids
Lymph- drains into vascular system

Question 12

Four types of immunoglobulin

Answer 12

IgM
IgG
IgE
IgA
Each type can bind to the same antigen (Ag)
The distribution of antibody and the effects of binding vary with the type.

Question 13

IgM come from and goes to

Answer 13

All B cells initially produce IgM
Then gradually switch to produce one of:
IgG
IgA
IgE

Question 14

IgM looks like

Answer 14

IgM looks like 5 Ig molecules joined together.
IgM is a big molecule so is mainly restricted to blood
Lots of binding sites (each one is weak)

Question 15

IgM does what

Answer 15

Protective actions
Efficient at agglutination (binding antigen together)
May precipitate antigens.

Question 16

Functions of IgM

Answer 16

Neutralization
Complement activation

Question 17

How does IgM neutralize

Answer 17

Binds to antigen making them ineffective
Pathogenic bacteria often have specialized structures so that they can attach to host cells.
Blocked by antibody.

Question 18

How is IgM part of complement activation

Answer 18

Classical pathway
Results in:
Inflammation (attractants for nutrophils)
Opsonization
Membrane attack complex

Question 19

IgG is produced when

Answer 19

As the immune response matures and becomes more efficient:
B cells switch from producing IgM to other Ig including IgG
In consequence, so do their plasma cells.
The major antibody of serum
Smaller than IgM so can reach sites of inflammation more easily
IgG is the principal antibody of tissue fluids.
Several sub-classes

Question 20

Function of IgG

Answer 20

Antibody defense
Agglutination of antigens
Neutralization
Complement activation
Opsonisation by direct binding
Antibody-dependent cell-mediated cytotoxicity

Question 21

How does IgG neutralize things

Answer 21

Binds much more tightly than IgM.
Blocks adhesion sites on pathogens
Bind and block toxins

Question 22

How does IgG do complement activation

Answer 22

Classical pathway.
Requires 2 IgG molecules to be bound close together

Question 23

How does IgG do opsonisation

Answer 23

Ig head binds to antigens e.g. on surface of bacteria
Ig tail changes shape
Can now bind to phagocytes.
Phagocytes engulf the antigen (e.g. bacteria) that the IgG is attached to

Question 24

Antibody dependent cell mediated cytotoxicity is done by IgG by

Answer 24

Some pathogens are just too big to be engulfed
Cells infected with virus.
Instead, antigen-IgG complexes bind to NK cells.
NK cell kills infected cell
Antigen-antibody complexes may also bind to neutrophils and eosinophils and stimulate them to release oxidants.

Question 25

Veterinary application of immunoglobulin

Answer 25

Serial measurements of Ig to determine if a pathogen is the underlying cause of clinical signs in the patient:
Serial Ig measurements
IgM will increase with acute infection, not if historically infected
IgG will increase during acute infection.
Titer testing for importation of animals- rabies

Question 26

IgA is and secreted by

Answer 26

IgA is the major antibody of mucosal surfaces ex. Gut, respiratory tract
Gut lymphoid tissue is a major site of IgA production.
Secreted as a dimer with secretory piece.
Transport tag for epithelial cells.
Confers resistance to digestive enzyme

Question 27

IgA works by

Answer 27

Works by neutralization
Viruses
Prevents microbes from binding to body surfaces
Agglutination
IgA cannot activate phagocytes (opsonize), does not bind complement.

Question 28

How much IgA is produced and where is it located

Answer 28

More Ig A produced in a day than all others combined.
Only a small amount in serum

Question 29

IgE is produced in

Answer 29

Produced by plasma cells just below body surfaces

Question 30

IgE works by

Answer 30

Most binds to surface of basophils and mast cells in tissues before it binds to antigen.
IgE is the sentinel antibody
Antigen binding causes release of granules
Triggers acute inflammation
Important in parasite defense
Important in allergies
Immediate hypersensitivity

Question 31

Free IgG is

Answer 31

Small amounts
Head of IgE binds to pathogens.
Parasites
Tail of IgE-Ag complex attracts and binds eosinophils.
Release enzymes that digest parasite
Another example of antibody dependent cell cytotoxicity

Question 32

IgD is present in

Answer 32

Present in some, but not all domestic animals
Largely attached to B cells
Significant variations in structure between species

Question 33

Function of IgD

Answer 33

Function unknown
Suspected of aiding in regulation of B cell response.