Immunology Part III

Question 1

Where is the heavy chain of the antibody?

Answer 1

On the inside (two light chains branch off on outside)

Question 2

What holds together the hinge region of an antibody and the domains (bubbles)?

Answer 2

S-S disulfide bonds!

Question 3

What are the different kinds of H (heavy) chains?

Answer 3

Gamma (G), alpha (A), mu (M), epsilon (E), delta (D)

• It defines the class of antibody to which a molecule belongs & its biological properites
• A cell may class switch with heavy chains but its L chain will stay the same (ex: IgG to IgM)

Question 4

What are the different kinds of L (light) chains?

Answer 4

Kappa or lambda.

Question 5

What are the key structural features of IgG?

Answer 5

Two light chains, two heavy chain, one subunit, circle on bottom

Question 6

What are the key structural features of IgG3?

Answer 6

Like IgG except it has a much larger/longer hinge region (>10 disulfide bonds), better binder of complement due to its hinge region

Question 7

What are the key structural features of IgM?

Answer 7

5 Individual IgMs linked together by a J chain (looks like IgG X 5 in a circle)

Question 8

What are the key structural features of IgA?

Answer 8

Two individual IgA molecule linked together by their bottoms/constant regions, have a J chain and secretory component linking them together

Question 9

What are the key structural features of IgD?

Answer 9

Looks similar to IgG. Has small (one disulfide bone) hinge region. Only found on naive B cells, membrane bound, doesn’t play role at site of infection.

Question 10

What are the key structural features of IgE?

Answer 10

Looks similar to IgM but its always secreted in monomeric form. It has many carbohydrate units attached. One disulfide bond above CH2 and one bond below CH2.

Question 11

What is the Fab and Fc regions?

Answer 11

Fab - where the antigen binds - has one constant and one variable segment
Fc - constant region, bottom on antibody

Question 12

What is an allotype?

Answer 12

Minor allelic differences in the sequence of immunoglobulins between individuals (like eye and blood types differ). The allotropes you express are determined by your parents and pass in Mendelian fashion

Question 13

What is an idiotype?

Answer 13

Each antibody will have its unique combining region, made up of the CDR amino acids of its L and H chains. We call this unique structure an idiotype. [An idiotype is an antibody’s unique combining site considered as an antigen]

Question 14

What is valence?

Answer 14

Refers to the number of antigenic determinants (epitopes) an antibody molecule can theoretically bind

Question 15

What is the valence of IgG?

Answer 15

2

Question 16

What is the valence of IgA?

Answer 16

4

Question 17

What is the valence of IgM?

Answer 17

10 - truth is it puckers so it can only take 5

Question 18

Valence of Fab?

Answer 18

1

Question 19

Valence of F(ab’)?

Answer 19

2

Question 20

Valence of VL or VH?

Answer 20

0 - you need the combination to make a binding site

Question 21

What are the relative concentrations of antibodies in the serum?

Answer 21

IgG - 1000 mg/dL (most common!)
IgA - 200 mg/dL
IgM - 100 mg/dL
IgD - 5 mg/dL
IgE - 0.02 mg/dL 
Order is: GAM-DE

Question 22

What antibodies usually activate complement (classical) pathway?

Answer 22

IgG or IgM

Question 23

What is the general function of IgG isotype?

Answer 23

Main antibody in blood and tissue fluids. It neutralizes toxins and blood-borne viruses, binds bacteria and facilitates their destruction by activating complement and by binding them to phagocytic cells.

Question 24

What is the general function of IgA isotype?

Answer 24

Can do similar things in the blood as IgG, but its real role is as the dimer form in secretions, where secretory component protects it from proteolysis.

Question 25

What is the general function of IgM isotype?

Answer 25

It does much the same as IgG. It is the first Ab to appear in the serum after immunization and it is very efficient at activating complement.

Question 26

What is the general function of IgD isotype?

Answer 26

Role in blood, if any, is uncertain. It seems to function as a receptor on naive B cells

Question 27

What is the general role of IgE isotype?

Answer 27

The antibody which causes Type I immunopathology, also called immediate hypersensitivity or allergy. -It's true importance is in resistance to worms and other parasites.

Question 28

What two cytokines are required to move from Hematopoietic Stem Cell to Lymphoid progenitor cell?

Answer 28

IL-7 and IL-3

Question 29

What is the B7 receptor also called?

Answer 29

``` B7-1 = CD80 B7-2 = CD86 ```

Question 30

What's present at the immunological synapse?

Answer 30

T cell binding APC. B7 on APC binds CD28 on T cell. MHC on APC binds TCR on T cell (CD3 & CD4). LFA 1 & 2 on T cell binds ICAM-1/3 on APC.

Question 31

What antibody isotype has the highest serum half life?

Answer 31

IgG

Question 32

What antibody isotype can cross the placenta?

Answer 32

IgG

Question 33

What antibody isotype is best at complement fixation?

Answer 33

IgM (and a little IgG)

Question 34

What antibody isotype does mast cell/basophil degranulation?

Answer 34

IgE

Question 35

What antibody isotype does Bacterial Lysis?

Answer 35

IgM (tiny bit of IgG and IgA)

Question 36

What antibody isotype does antiviral activity?

Answer 36

IgA (little IgM and IgG)

Question 37

What antibody isotype does toxin neutralization?

Answer 37

IgG and IgA

Question 38

What antibody has a serum half-life of 8-23 days?

Answer 38

IgG

Question 39

What is the biological function of IgM?

Answer 39

- Excellent at agglutination and precipitation of antigens - As a monomer it can serve as a surface receptor for antigens on B cells (like IgD) - Elevated levels indicate a recent infection or other exposure to antigen - Can be present in bodily secretions

Question 40

What is the biological function of IgG (IMPORTANT)?

Answer 40

- Good at agglutination and precipitation of antigens - Binds to macrophage Fc receptors - Can mediate hemolytic disease of the newborn (blue baby syndrome, Rh) - Can be used to protect immunocompromised individuals (gamma globulin) - Can be used as a blocking antibody to block TNF production (RA)

Question 41

What is the biological function of IgA (IMP)?

Answer 41

- Good at agglutination and precipitation of antigens - Daily production of IgA is greater than any other Ig - Present in bodily secretions - Present at very high level in colostrum and present in breast milk - Provides excellent level of protection for newborns against resp. and intestinal infections

Question 42

What is the biological function of IgE?

Answer 42

- Cross-linking of IgE surface molecules on the surface of mast cell or basophil causes the release of histamine; the synthesis of prostaglandins, leukotrienes, etc. - Plays role in combating parasitic and pulmonary fungal infections - Individuals who express allergies to certain antigens over-produce IgE to those antigens - Many mast cells are degranulate, resulting in over-stimulation of the immune system that is manifested as an allergic reaction (Type I hypersensitivity) - IgE also plays a role in asthma