Adaptive Immunity: Humoral Response Flashcards
What are the two responses of adaptive immunity?
- Humoral response (antibody response)
- Cell-mediated Response
What type of cell / lymphocyte produces immunoglobulins?
B cells
free-floating Y-shaped immunoglobulins
antibodies
What are the 3 functions of antibodies?
- neutralization
- opsonization
- complement activation
the selection of the small subset of pathogen-specific lymphocytes for proliferation and differentiation into effector lymphocytes
clonal selection and expansion
When an antibody is divided by the flexible hinge region, the two upper components are called the ____.
Fab (fragment antigen binding)
When an antibody is divided by the flexible hinge region, the one lower component is called the ____.
Fc (fragment crystallizable)
ends of the variable region chains of antibodies
N termini
end of the constant region chain of antibodies
C termini
The _____ region of the antibody binds to the macrophage receptors.
constant region
The ____ region of the antibody serves as antigen-binding site
variable region
the part of the pathogen that antibodies recognize
epitope
two types of epitopes
linear or discontinuous
tips of the variable regions that show high variability and provide a binding surface that is complementary to that of the antigen
hypervariable region / complementarity-determining region (CDR)
less variable regions that support the hypervariable region
framework regions
binding strength of a single antigen binding site to antigen
affinity
binding strength of multiple antigen binding sites to antigen
avidity
Binding to antigen depends on 4 non-covalent bonds, namely _____
- Van der Waals forces
- Hydrophobic bonds
- Electrostatic bonds
- Hydrogen bonds
The different antibody isotypes depends on the structure of the ____ region.
constant region
What are the 5 different antibody isotypes?
IgG, IgM, IgD, IgA, IgE
What 4 factors form the genetic basis of antibody diversity?
- combinatorial diversity / somatic recombination
- junctional diversity
- heavy and light chain V region combinations
- somatic hypermutation
In a developing B cell, the process of immunoglobulin-gene rearrangement is tightly controlled so that only one heavy chain and one light chain are finally expressed, a phenomenon known as _______.
allelic exclusion
process wherein the arrays of V, D, and J segments of the heavy chain V region are cut and re-spliced by DNA recombination
somatic recombination
sequences that direct the recombination of V, J, and D gene segments
recombination signal sequences (RSSs)
set of enzymes needed to recombine V, D, and J segments
V(D)J recombinase
What is the 12/23 Rule?
segments with a 12 bp spacer RSS can only be joined with a segment with a 23 bp spacer RSS
hold RSS in place while genes are recombined and clips V and J segments closer together so they can be cut out
RAG complexes (recombination activating genes)
What happens when the RAG complex opens up DNA hairpins?
palindromic P-nucleotide sequences are formed
adds random N-nucleotides to ends of P-nucleotide sequences
TdT (terminal deoxynucleotidyl transferase)
removes unpaired nucleotides
exonuclease
Which gene segment/s code for CDR1 and CDR2?
V gene segments (light and heavy)
Which gene segments code for CDR3?
VJ junctional diversity (light), D segment + VJ junctional diversity (heavy)
What type of C terminus do transmembrane immunoglobulins have?
hydrophobic
What type of C terminus do free-floating/secreted immunoglobulins have?
hydrophilic
replaces cytosine with uracil in somatic hypermutation
activation-induced cytidine deaminase (AID)
removes uracil in somatic hypermutation
uracil-DNA glycosylase (UNG)
replaces removed uracils with random nucleotides which serve as the source of somatic hypermutation
DNA polymerases
____ gene segment are closest to V, D, and J segments by default
Cµ and Cδ
signals for isotype switching; highly repetitive sequences that mediate recombination
switch regions / genes
first antibody made in primary immune response
IgM
Switch sequences flank the __’ side of each C gene
5’
endonuclease that excises abasic nucleotide resulting from removal of uracil by UNG
APE1
Ig that has low affinity and exists in a bulky pentameric form
IgM
Ig that targets parasites and triggers asthma and allergic reactions
IgE
most commonly circulating Ig in the bloodstream
IgG
Ig mostly found in respiratory tract
IgD
Ig associated with mucosal membranes; exists in monomeric and dimeric forms
IgA
most abundant type of IgG and binds to protein antigens
IgG1
most abundant type of IgG and binds to protein antigens
IgG1
second most abundant type of IgG that targets carbohydrates
IgG2
type of IgG that is most susceptible to proteases but is best at activating complement
IgG3
least abundant type of IgG and plays an important role in reducing allergic reactions
IgG4
antibodies coupled with chromophores or fluorophores
antibody conjugates
type of antibody conjugate where the primary antibody is directly conjugated to a fluorophore
direct antibody conjugate
type of antibody conjugate where fluorophore-conjugated secondary antibody is directed against unconjugated primary antibody
indirect antibody conjugate
multiple antibodies produced targeting the same antigen but different epitopes or parts of the antigen
polyclonal
antibodies specifically target the same epitope of same antigen
monoclonal
ELISA
enzyme linked immunosorbent assay
IFAT
immunofluorescence antibody technique
4 main steps for antibody-based methods
- antigen coat over inert surface
- add blocking solution
- antibody incubation
- antibody visualization
examples of blocking solutions
3% skim milk, 1% bovine serum albumin
ELISA antibody conjugates
horseradish peroxidase, alkaline phosphatase
IFAT antibody conjugates
fluorescein isothiocyanate
