Immunology Part III Flashcards
Where is the heavy chain of the antibody?
On the inside (two light chains branch off on outside)
What holds together the hinge region of an antibody and the domains (bubbles)?
S-S disulfide bonds!
What are the different kinds of H (heavy) chains?
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)
What are the different kinds of L (light) chains?
Kappa or lambda.
What are the key structural features of IgG?
Two light chains, two heavy chain, one subunit, circle on bottom
What are the key structural features of IgG3?
Like IgG except it has a much larger/longer hinge region (>10 disulfide bonds), better binder of complement due to its hinge region
What are the key structural features of IgM?
5 Individual IgMs linked together by a J chain (looks like IgG X 5 in a circle)
What are the key structural features of IgA?
Two individual IgA molecule linked together by their bottoms/constant regions, have a J chain and secretory component linking them together
What are the key structural features of IgD?
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.
What are the key structural features of IgE?
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.
What is the Fab and Fc regions?
Fab - where the antigen binds - has one constant and one variable segment
Fc - constant region, bottom on antibody
What is an allotype?
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
What is an idiotype?
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]
What is valence?
Refers to the number of antigenic determinants (epitopes) an antibody molecule can theoretically bind
What is the valence of IgG?
2
What is the valence of IgA?
4
What is the valence of IgM?
10 - truth is it puckers so it can only take 5
Valence of Fab?
1
Valence of F(ab’)?
2
Valence of VL or VH?
0 - you need the combination to make a binding site
What are the relative concentrations of antibodies in the serum?
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
What antibodies usually activate complement (classical) pathway?
IgG or IgM
What is the general function of IgG isotype?
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.
What is the general function of IgA isotype?
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.
What is the general function of IgM isotype?
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.
What is the general function of IgD isotype?
Role in blood, if any, is uncertain. It seems to function as a receptor on naive B cells
What is the general role of IgE isotype?
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.
What two cytokines are required to move from Hematopoietic Stem Cell to Lymphoid progenitor cell?
IL-7 and IL-3
What is the B7 receptor also called?
B7-1 = CD80 B7-2 = CD86
What’s present at the immunological synapse?
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.
What antibody isotype has the highest serum half life?
IgG
What antibody isotype can cross the placenta?
IgG
What antibody isotype is best at complement fixation?
IgM (and a little IgG)
What antibody isotype does mast cell/basophil degranulation?
IgE
What antibody isotype does Bacterial Lysis?
IgM (tiny bit of IgG and IgA)
What antibody isotype does antiviral activity?
IgA (little IgM and IgG)
What antibody isotype does toxin neutralization?
IgG and IgA
What antibody has a serum half-life of 8-23 days?
IgG
What is the biological function of IgM?
- 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
What is the biological function of IgG (IMPORTANT)?
- 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)
What is the biological function of IgA (IMP)?
- 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
What is the biological function of IgE?
- 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
