Antibodies 1/3 Flashcards
How are Antibodies created?
“Stimulation of B lymphocytes by antigens causes the cell to undergo
proliferation and differentiation = end product is an antibody (or
immunoglobulin) “
Antibody importance to immunity
“Major component of humoral adaptive immunity
•Role in antigen recognition and in biological activities related to the
immune response (ex. opsonization)
“
Antibody presence in blood
- Found in serum
- Liquid part of blood without clotting factors
- Serum with known antibodies against a particular antigen = antiserum
Main functions of antibodies
“Neutralization of microbes and toxins
Opsonization and phagocytosis of microbes
Antibody-dependent cellular cytotoxicity
Lysis of microbes
Phagocytosis of microbes opsonized with complement fragments
Inflammation
Complement activation “
How do antibodies neutralize microbes or toxins?
“Without AB : infection of cell by microbe -> release of microbe from infected cell and infection of adjacent cell -> pathologic effect of toxin
With AB : Antibody blocks binding of microbe and infection of cell -> Antibody blocks infection of adjacent cell-> Ab block binding of toxin to cellular receptor “
What is Viral Neutralization?
“ABs neutralize (decrease the replication of) viruses by :
- AB blocks binding of microbe and infection of the cell
- Antibody blocks infection of adjacent cell
- AB blocks binding of toxin to cellular receptor”
How does opsonization and phagocytosis apply to ABs?
“Opsonization of microbe (cover microbe) in IgG
- Bind opsonized microbes to phagocyte Fc receptors
- Fc receptor signals activate phagocyte
- Killing of injested microbe
( cover microbe in IgG -> phagocyte sees and binds microbe -> Fc (from binding) activates phagocyte -> phagocytosis and killing of ingested microbe) “
What is the role of ABs in AB-dependent cellular cytotoxicity?
“Antibody binds antigens on surface of target cells
- Fc receptors on NK cell recognize bound antibody
- cross-linking of Fc receptors signals the NK cell to kill the target cell
- Target cell dies by apoptosis”
How do AB activate complement?
“IgG molecules bind to antigens on bacterial surface -> C1q binds to 2+ of IgG molecules and initiates complement activation
IgM molecules bind to soluble multivalent antigen -> C1q binds to soluble immune complex and initiates complement activation “
General antibody structure consists of
”- basic 4-chain polypeptide unit + disulfide bonds
= 2 large/Heavy(h-chain) + 2 smaller/light(l-chain)
also has 2 regions (variable + constant) + hinge “
What is the difference between the types of chains in ABs
“Large/Heavy/H-chain - 5 types (alpha, gamma, delta, epsilon, mu)
Smaller/Light/L-chain - 2 types (Kappa, lambda) “
Compare the Variable and Constant regions
“V - allows for antigen-binding
C - (CH1,2,3) unique to each Ab class”
Isotype AB
"Unique chains for each Ig; unique amino acid sequence that is common to all Ig molecules of a given class in a given species IgG - gamma, IgA - alpha, IgE - epsilon, IgM - mu, IgD - delta * refers to constant region of H chain "
Allotype AB
“Minor variations of amino acid sequences that are present in some individuals but not others
- seen in 4 IgG subclasses, IgA subclass, K L chain
- Found in constant region and inherited in Mendelin fashion “
Idiotype AB
“Variable portions of each chain, unique to a specific Ab molecule
- Amino-termninal ends of both L and H chains -> antigen-recognition unit “
