antibodies Flashcards
(19 cards)
What are the three hypervariable regions found within each V_H and V_L domain of antibodies?
They are regions that contribute to the diversity of antibody specificity
These regions allow for the generation of a vast array of antibody specificities.
Approximately how many different antibody specificities can an individual generate?
~10^8 different Ab specificities
This diversity arises from the recombination of gene segments encoding antibody chains.
What is the central dogma of biology regarding gene expression?
1 gene => 1 mRNA => 1 polypeptide
This concept was the prevailing view until research in the 1970s revealed complexities in antibody gene encoding.
How many gene segments encode the light and heavy chains of antibodies?
Light chain: 3 gene segments; Heavy chain: 4 gene segments
This allows the generation of a diverse antibody repertoire from a limited number of genes.
What does ‘GOD’ stand for in the context of antibody diversity?
Generation of Antibody diversity
This term refers to the mechanisms by which the immune system produces a wide variety of antibodies.
How many classes (isotypes) of antibodies are there?
5 different classes (isotypes) of antibody
The isotypes are determined by the heavy chain present in the antibody structure.
What are the five classes of antibodies?
- IgA
- IgD
- IgE
- IgG
- IgM
Each class has distinct functions and locations within the body.
What are the two types of light chains in antibodies?
- Kappa (k)
- Lambda (l)
The type of light chain can influence the antibody’s function and characteristics.
What is the major Ig class of the primary immune response?
IgM
IgM is characterized by its large size and is primarily found in the vascular system.
What is the major Ig class of the secondary immune response?
IgG
IgG constitutes about 70% of total Ig in the bloodstream and can cross capillary walls.
What is the half-life of IgA in serum?
~6 days
IgA exists in both monomeric and dimeric forms, with dimeric IgA being predominant in secretions.
Where is dimeric IgA primarily found?
In sero-mucus secretions (e.g., saliva, gut, airways)
Dimeric IgA plays a crucial role in mucosal immunity.
What is the primary role of all classes of antibodies?
Specific binding to antigens (Ag)
This binding initiates various immune responses.
List some secondary roles of antibodies.
- Ag receptor on B cell
- Agglutination/precipitation of Ag
- Opsonization of Ag
- Neutralization of microbial toxins
- Preventing microbe attachment
- Activation of complement cascade
- Ab-dependent cell-mediated cytotoxicity (ADCC)
- Triggering mast cell degranulation
- Passive immunity for offspring
These roles enhance the immune response and help protect against pathogens.
What is opsonization?
Tagging Ag target with Ab to enhance phagocytosis
The Fc region of the antibody binds to Fc receptors on phagocytes, facilitating the uptake of pathogens.
What is the role of IgE in the immune system?
Triggering degranulation of antigen-sensitized mast cells
IgE is involved in hypersensitivity reactions and allergic responses.
What is the significance of the neonatal Fc receptor (FcRn) in antibody transfer?
Facilitates the transfer of maternal IgG to the fetus across the placenta
This process is crucial for passive immunity in newborns.
What does passive immunity for offspring entail?
Transfer of maternal antibodies to the fetus/neonate
This transfer occurs via the placenta and breast milk, providing early protection against infections.
What is the role of complement activation in the immune response?
Enhances opsonization and promotes inflammation
The complement system plays a critical role in the clearance of pathogens.
