MI 02b: Ab and TCRs Flashcards
Antibody, aka an (X) molecule/monomer, has (Y) structure.
X = Ig Y = hetero-tetramer
Ab has (X) heavy and (Y) light chains that are (non-covalently/covalently) joined by (Z) bonds.
X = Y = 2
Covalently;
Z = disulfide
At the (carboxyl/amino) terminal end of (heavy/light) chains is the “variable” region of Ab.
Amino;
Both heavy and light chains
At the (carboxyl/amino) terminal end of (heavy/light) chains is the “constant” region of Ab.
Caroxyl;
Both heavy and light chains
Within (X) region of Ab, there are (2/3/4/5) stretches of (Y) that exhibit even greater degrees of variability between Ab molecules. What are these regions called?
X = variable
3;
Y = AA
Hypervariable regions or complementarity-determining regions (CDR1, CDR2, CDR3)
Which region(s) on Ab are in contact/complementary to the antigen?
Hyper-variable regions (CDR1, 2, and 3)
The (X) of the (H/L) chain of Ab determines the isotype.
X = AA sequence of constant region
H chain
In humans, there are (X) number of Ab isotypes that are placed into (Y) number of classes. List the classes. Star those with subclasses.
X = 9 Y = 5
IgM, IgA, IgD, IgG, IgE
All cell surface Ig classes are (mono/di/tri/tetra)-mers and anchored to the membrane through (C/N) terminus of (H/L) chain.
monomers;
C;
H
In soluble form, which Ig classes are monomers?
IgD, IgG, IgE
In soluble form, which Ig classes are dimers?
IgA
In soluble form, which Ig classes are tetramers?
None
In soluble form, which Ig classes are pentamers?
IgM
In soluble form, the Ig classes that aren’t monomers are held together by:
J chain
In soluble Ab, the (Fab/Fc) region is responsible for mediating effector functions, aka recruitment of (X), when the (Fab/Fc) region is (bound/unbound) to (Y).
Fc; X = innate immune forces Fab; Bound X = complementary antigen
The TCR has (X) structure, composed of which chain(s)?
X = heterodimer
One alpha and one beta chains
In TCR structure, (alpha/beta) chain consists of (N/C) variable region.
Both; N-terminal
In TCR structure, (alpha/beta) chain consists of (N/C) constant region.
Both; C-terminal
In TCR structure, (constant/variable) region traverses the (X) cell membrane.
Constant (C-terminal);
X = T cell
T/F: CDR1, 2, and 3 hypervariable regions are exclusively found on Ab.
False
Variable region of TCR contains which (if any) hypervariable regions?
CDR1, 2, and 3 (like Ab)
T/F: A minority of TCRs are made up of gamma and delta chains.
True (5-10%)
What’s an epitope?
Part of antigen that contacts the antigen receptor
T/F: BCRs and TCRs recognize different types and forms of antigens.
True
In soluble form, TCR forms (mono/di/tri)mer?
NEVER secreted in soluble form! Only on cell surface
(BCR/TCR)s can recognize any chemical structure in its native form.
BCRs
(BCR/TCR)s are high-maintenance. They only interact with (X)-derived (Y) that are presented in context of (Z).
TCRs;
X = antigen
Y = peptides
Z = self-MHC molecules
In general, TCRs CDR1 region interacts with:
MHC molecule
In general, TCRs CDR2 region interacts with:
MHC molecule
In general, TCRs CDR3 region interacts with:
Peptide
T/F: MHC class I and II molecules are expressed on the same types of cells.
False
MHC Class I molecules are expressed on (X) cells.
X = all nucleated
MHC Class II molecules are expressed on (X) cells.
X = Antigen-presenting
and thymic epithelial cells
MHC Class I molecule has (X) chains with (Y) number of domains. It’s (covalently/non-covalently) associated with (Z).
X = one alpha
Y = 3
Non-covalently
Z = beta-2-microglobulin (beta-2m) protein
MHC Class II molecule has (X) chains with (Y) number of domains. Its (covalently/non-covalently) associations form which structure?
X = one alpha and one beta
Y = 2 domains on each chain
Non-covalently;
Heterodimer
MHC class (I/II) contain peptide-binding cleft.
Both
MHC Class I has peptide-binding cleft formed by (X) domain of (Y) chain.
X = first two Y = alpha
MHC Class II has peptide-binding cleft formed by (X) domain of (Y) chain.
X = first Y = both alpha and beta chains
The human MHC is also referred to as:
HLA (human leukocyte antigen)
How many loci encode distinct human MHC class I proteins? List them. What does each locus encode?
3 loci
HLA-A, HLA-B, HLA-C
Each locus encodes one alpha chain
How many loci encode distinct human MHC class II proteins? List them. What does each locus encode?
3 loci
HLA-DP, HLA-DQ, HLA-DR
Each locus encodes a distinct alpha and beta chain
We inherit (X) sets of MHC alleles from each parent.
X = one
T/F: The MHC loci are the most highly polymorphic loci in any mammalian genome.
True
The majority of polymorphic AA in MHC molecules are localized in which part of molecule?
Peptide-binding cleft
Each specific MHC molecule can bind peptides of (one/many) sequence(s) and (one/multiple) peptides at a time.
Many;
one
What can you say about all peptides that can bind to one specific MHC molecule? Be specific.
They share structural features (similar AA residues at critical positions)
What’s the formal name of AA residues in critical positions that allow peptide to fit into binding pockets of MHC cleft.
Anchor residues
AA residues on peptide that face away from MHC molecule interact with (X) and are thus called (Y).
X = TCR Y = TCR contact residues
One individual will inherit (X) different MHC class I alleles from each parent.
X = 3
One individual will inherit (X) different MHC class II alleles from each parent.
X = 3
What determines which MHC Class I or II allele (from mom or dad) will be expressed on a given cell?
All alleles are expressed co-dominantly!
Every individual is capable of producing (X) different MHC Class I proteins and (Y) different MHC Class II proteins.
X = 6; Y = 12
The disparity in (X) between individuals is the greatest contributor to rejection in organ/tissue transplantation.
X = MHC sequences
MHC Class I molecules present (X) to which specific type of (Y) cells?
X = antigen-derived peptide
CD-8
Y = T cells
MHC Class II molecules present (X) to which specific type of (Y) cells?
X = antigen-derived peptide
CD-4
Y = T cells
The function of CD4/8 molecules, aka (X), on (Y) cells is to:
X = co-receptors Y = T
Enhance avidity of TCR:MHC binding
CD4/8 molecules interact with which specific regions of (X)?
X = MHC molecules
Non-polymorphic regions
MHC Class I pathway presents peptides derived from (intra/extra)-cellular pathogens.
Intracellular
MHC Class II pathway presents peptides derived from (intra/extra)-cellular pathogens.
Extracellular (phagocytosed/endocytosed)
MHC Class (I/II) pathway: the cytosolic protein is degraded into peptides by (X). The peptides are then transported across (Y) via (Z).
Class I;
X = proteosome
Y = ER membrane
Z = TAP (transporter)
MHC Class (I/II) pathway: within ER, peptides are preferentially associated with newly synthesized (Y).
Class I
Y = MHC Class I proteins
MHC Class (I/II) pathway: the engulfed microbe is degraded into peptides by (X). The peptides are then transported across ER via (Y).
Class II
X = proteases (in lysosome)
NOT transported to ER!
T/F: Both MHC Class I and II proteins are transported through the ER.
True
(Inside/outside) ER, MHC Class (I/II) proteins are bound to (X), occluding the (Y).
Inside;
Class II
X = invariant chain (Ii) protein
Y = peptide-binding cleft
The invariant chain (Ii) protein prevents (intra/extra)-cellularly derived peptides from binding to the MHC Class (I/II) proteins.
Intracellularly
Class II
An extracellular pathogen engulfed by macrophage will eventually activate (CD4/CD8) T cell, which functions to (X) by (Y).
CD4 (helper T cell);
X = help macrophage kill ingested microbe
Y = secreting cytokines
An extracellular pathogen endocytosed by B cell will eventually activate (CD4/CD8) T cell, which functions to (X) by (Y).
CD4 (helper T cell);
X = stimulate B cells to produce Ab (to attack extracellular pathogen)
Y = secreting cytokines
An intracellular pathogen are presented by (X) and will eventually activate (CD4/CD8) T cell, which functions to (Y).
X = MHC Class I proteins
CD8;
Y = kill infected cell
