Immunology Exam 2 (Complement, Ags/Abs, Cytokines, MHC) Flashcards
Five major classes of antibodies in order of abundance
IgG, IgA, IgM, IgD, IgE
What is the key element of the humoral immune response?
Antibodies
Isotypes
Unique amino acid sequence common to all antibodies of a given class, identical in all individuals of a species and differ between species (IgG is an isotype)
Allotypes
Minor variations of amino acid sequences that are present in some individuals of the same species, but not all
(Such as IgG1, IgA2)
Idiotypes
Variations in variable regions that give individual antibody molecules specificity (Binds to the antigen, different)
Where do antibodies appear on serum electrophoresis?
Gamma band at pH 8.6
What are antibodies held together by?
Noncovalent forces and disulfide interchain bridges
Basic structure of an antibody
2 heavy chains
2 light chains
Fab region at the Y
Fc region at straight part of Y
Purpose of the Fc region
Has no antigen-binding ability
Can bind complement and important for opsonization
White cells that have Fc regions would be which cells?
Neutrophils and monocytes (opsonization –> phagocytosis)
Where are light chains located on an antibody?
Outside portions of the “Y” structure
Purpose of the Fab region
Binds antigens (2 binding sites per Fab region)
Which part of an antibody is obtained by papain digestion?
2 Fab fragments and one Fc fragment, horizontal cut
Which part of an antibody is obtained by pepsin digestion?
F(ab’)2, vertical cut, Fc portion in nonfunctional pieces
What are Bence Jones Proteins?
Light chains, kappa and lambda
Can be secreted by malignant plasma cells and associated with multiple myeloma
What disease states are associated with Bence Jones Proteins?
Multiple myeloma
Heat shock (goes back to normal)
What is unique to each class and gives each immunoglobulin type its name?
Heavy chains
What heavy chain is on an IgG?
gamma chain
What heavy chain is on IgA?
alpha chain
What heavy chain is on IgD?
Delta chain
What heavy chain is on IgE?
Epsilon chain
What heavy chain is on IgM?
Mu chain
What is the hinge region?
The segment of heavy chain located between CH1 and CH2 regions - disulfide bonds
What has a high content of proline, allowing flexibility, and hydrophobic residues?
Hinge region
What allows two antigen-binding sites to operate independently and assists initiation of complement cascade?
Hinge region
What has the longest half life of any Ig?
IgG, 23 days
What IgG molecules are best at activating complement?
IgG3 is the best, then IgG1
Most predominant allotype of IgG
IgG1
Why is IgG3 the best at activating complement?
Super long hinge region
What IgG allotypes are poor mediators of complement activation and why?
IgG2 and IgG4 ; they have shorter hinge segments
Major functions of IgG
Provide immunity for newborn (can cross placenta)
Activates complement
Opsonization
Neutralizing toxins and viruses
Agglutination/Precipitation rxn
T/F: All allotypes of IgG can cross the placenta.
True
T/F: IgG is better at agglutination reactions than at precipitation reactions.
False. IgG is better at precipitation reactions
What is the half life of IgM?
6 days
Where is IgM found as a monomer? Where is IgM found as a pentamer?
Monomer: on surface of B cells
Pentamer: secretions
Which Ig molecule is known as the macroglobulin?
IgM
How many binding sites does IgM have?
5
Which antibody has a high valency, high affinity, low avidity?
IgM
T/F: IgM has memory cells
False
Functions of IgM
Complement fixation
Agglutination
Neutralization
Primary Response Antibody
Opsonization
What is known as the primary response antibody?
IgM
Where is IgA1 found?
Blood
Where is IgA2 found?
Mucosal surfaces
Secretory IgA functions
- Patrols mucosal surfaces and acts as a first line of defence
- Passively transfers immunity to newborn during breastfeeding
- Indirectly activate complement
What cells possess specific receptors for serum and secretory IgA?
Neutrophils, monocytes, and macrophages
What Ig is on the surface of B cells only?
IgD
What Ig attaches to basophils and eosinophils and tissue mast cells?
IgE
What Ig has to do with allergic reactions?
IgE