Antibodies Flashcards
Immunoglobulin G molecules from two different individuals represent two different ————- of the same class of imunoglobulins (e.g. IgE) beacuse they are encoded by two different alleles of the same gene
Allotypes
—————– Are determined from allelic differences in the same antibody isotypes that differ between people
Allotypes
* Antibody isotypes (IgG, IgM, IgA, IgE, IgD)
The isotype of an antibody is determined by the constant regions of the light chain or heavy chain?
heavy chains
The unique structure of the antigen binding site created by the variable regions of the light and heavy chains is called the ————– of the antibody
Idiotype
Two antibodies of the same allotype and isotype that bind different antigens are different ———– .
Idiotypes
What region of the antibody accounts for the unique antigen binding sit, which ultimately distinguishes between idiotypes?
Variable region
Which immunoglobulin fixes complement,crosses the placenta, Opsonizes bacteria, and neutralizes bacteria toxins and viruses?
IgG
Which immunoglobulin prevents the attachment of bacteria and viruses to mucous membranes but cannot fix complement?
IgA
Which immunoglobulin is found in secretions?
IgA
What is the structure of Immunoglobulin A in secretions?
Dimer
What is the structure of Immunoglobuline M ?
Pentamer/ Monomor
Which immunoglobuline is produced as part of the primary response to an antigen, fixes complement, but does not cross the placenta?
IgM
Which immunoglobulin has an unclear fxn and can be found on the surface of B cells and in serum?
IgD
Which immunoglobulin is the antigen receptor on the surface of B cells?
IgM
Which immunoglobulin induces the release of mediators from mast cells and basophils when an individual is exposed to an allergen?
IgE
Which immunoglobuline mediates immunity to helminths and protozoa?
IgE
Which type of Antibody activates Eosinophils?
IgE
* It also activates mast cells and basophils
which 2 immunoglobulins are joined by J chains?
IgA and IgM
The 5 isotypes of the Heavy (H) chains
α, γ, ε, δ, μ
the 2 isotypes of the light (L) chains
κ, λ
Fxn of the Fab regions
The Fab regions bind to antigens -mediate Ag recognition
fxn of the Fc region
the Fc region of the antigen-couples antibody binds to molecules (e.g. C1q) or Fc receptors on cells - mediates effector functions
What are FcRs and their fxn?
FcRs –> Fc receptors
they mediate many effector fxns of antibodies by binding to the Fc portion of the Abs
what cells express FcRs ?
Immune cells, Epithelial cells, and endothelial cells
Most diverse group of FcRs?
FcγRs
* the main mediators of antibody functions in the body
What immunoglobuline do FcγRs bind to?
IgG
If FcγRs are expressed by phagocytic cells (macrophages) they will induce —————-
phagocytosis (Opsonisation)
If FcγRs are expressed by cytotoxic cells (NK cells) they will induce —————- upon binding to IgG-antigen complexes
ADCC- antibody dependent cell mediated cytotoxicity
Fc receptor expressed by NK cells
FcγRIII (CD16)
Explain how FcγRs on NK cells induce
antibody-dependent cell-mediated cytotoxicity (ADCC) of antibody-coated target cells
Ab binding to FcγRIII (CD16) on NK cells –> directs the cytotoxic activity to a specific cellular target (Viral infected cells)
What Fc receptor is Often associated w/ allergy symptoms and is expressed by mast cells/ basophils and eosinophils ?
FcεR
FcεR Upon binding to ——————– it triggers a signaling cascade that results in degranulation and release of histamine, proteases, and other inflammatory mediators
IgE-antigen complexess
Fc receptor expressed by Epithelial cells?
pIgR - Polymeric immunoglobulin receptor
Fxn of PIgR receptors?
- Transport of IgA and IgM from blood to the lumen of multiple tissues (Gastrointestinal, Respiratory, Reproductive tract)
- Responsible for carrying IgA into body secretions: tears and milk
- Responsible for the transfer of IgA to gut mucosa to protect against ingested microbes and toxins
Fxn of FcRn in children vs adults
*Neonatal
Children: carries antibody ingested in mother’s milk across epithelial cells of the intestine into the bloodstream
Adults: , its expression on cells that line the bloodstream helps to maintain IgG levels in serum by protecting them from degradation
FcRn receptor are expressed by?
epithelial cells and endothelial cells
