Antibody Structure Flashcards
What is the composition of blood?
plasma ~ 55%
“buffy coat” = leukocytes and platelets <1%
erythrocytes ~45%
What is serum?
Plasma - clotting factors (serum still contains the antibodies)
What is plasma?
The light yellow liquid part of blood containing water, salts, enzymes and cellular waste products
What makes the structure of an antibody?
2 heavy chains (~450-550 aa) and 2 light chains (~200 aa, kappa or lambda)
2 variable regions at the amino terminus on both the heavy and light chains, making 4 total
2 constant regions at the carboxy terminus, making 4 total
2 Fab regions
2 Fc regions
What is the Fab antibody region?
= Fragment antigen binding - includes heavy and light chain variable regions plus the constant light region and part of the constant heavy regions. Each has 1 antigen binding site. There are 2 Ag binding sites on each Ab
What is the Fc antibody region?
=Fragment crystallizable. The tail (stalk) region of an antibody that interacts with cell surface receptors (FcRs) and some complement system proteins. Allows antibodies to activate the immune system and have effector functions
Explain the epitope region
The part of the Ag recognized by the immune system where the Ab binds
Mediated by non-covalent bonds (H bonds, ionic, hydrophobic)
How many hypervariable regions are in the variable region of an Ab and what is another name for them?
AKA complimentary determining regions (CDRs)
Each variable region is made of 3 hypervariable regions : CDR1, CDR2 and CDR3
How many hypervariable regions are on each Ag receptor?
6 for each Ag receptor: 3 on the heavy variable region, 3 on the light variable region
What is an isotype?
Antibody categorization based on differing heavy chain constant regions
What are the different isotypes in humans?
IgG IgA IgM IgE IgD
What are some characteristics of IgG?
The most abundant isotype
Predominant in the secondary response
4 subtypes that differ in the flexible hinge length
What are some characteristics of IgA?
Dimer with 4 Ag binding sites
Primary isotype in secretions
Passive immunity in breast milk
Resistant to proteases
What are some characteristics of IgM?
Main isotype in the primary response
Pentamer with 10 identical Ag binding sites
What are some characteristics of IgE?
Helminth protection
Sensitizes mast cells and basophils, which lead to allery symptoms
