PCB 3233
PCB 3233 - Immunology Exam 3 with
Correct Answers 2026 Update
Helper T cells associate with which class of MHC molecules?
MHC Class 2 (extracellular infection)
BCR (B cell receptor) and TCR (T cell receptor), how are they created and where
in the body are they created?
As a result of Gene Arrangement (VDJ Somatic Recombination).
- BCR: produced in Bone Marrow
- TCR: produced in Thymus
Interferon function
Viral fighting, they activate NK cells which then tell our infected cells to die by
apoptosis.
BCR and TCR how are they created?
somatic recombination - gene rearrangement = sequence variability in V regions
(bone marrow vs. thymus)
What process creates the variable region domain for both TCRs and BCRs?
Somatic Recombination
Structure of immunoglobulin and the T cell receptor (TCR)?
Ig:
- Ig = Heavy and light chains, Fab and Fc regions, 4 polypeptide chains, secreted.
TCR:
- (alpha) chain and (beta) chain each with variability and constant region.
- TCR = α and β chains, 2 polypeptide chains, CD3 complex (4 proteins for
signaling), 2 zeta chains, transmembrane.
Each chain has a variable and a constant region
What the different types IFN-1?
Alpha and Beta
PCB 3233
,PCB 3233
structure of immunoglobulin and the TCR
a. BCR: 4 polypeptide chain with a and b for signalling on the surface of a B cell
b. Domain structure of TCR is similar to lg
c. TCR: 2 polypeptide, CD3 complex (4 proteins for signaling), and 2 zeta chains
d. each chain has variable region and constant region
What are the differences and similarities between CD8 T Cells and NK cells?
The both have the same cytotoxic granules, NK cells are activated faster,
because they come out of the bone marrow "ready to go". CD8 T cells recognizes
MHC Class 1 + peptide (antigen) on a pathogen, while NK cells recognize normal
MHC Class 1 molecules on the surface of our cells and activating ligands that
infected cells put up on their surface.
The T cell receptor (TCR) type of antigen vs. Ig (BCR) type of antigen?
a) TCR
TCR:
- bind to peptide antigens which are derived from the pathogen's proteins.
- It requires presentation by MHC molecules.
- Cells bind one type of antigen which must be presented to them on the surface
of another human cell.
2 types of activating ligands
MIC - A and MIC - B, they bind to activating receptors on activating NK cells
The TCR type of antigen vs. lg type of antigen.
a. TCR only found on the surface of their t cells; multipoint attachement;
multiple copies of TCR bind to multiple copies of antigen (MHC complex on
opposing cell)
b. BCR can be secreted in the form of an antibody; bind epitopes on intact
molecules
Type 2 interferon
Also know as IFN- gamma, activates macrophages
The T cell receptor (TCR) type of antigen vs. Ig (BCR) type of antigen?
b) BCR
PCB 3233
,PCB 3233
BCR:
- bind intact molecules and DO NOT require presentation.
- bind to proteins/carbohydrates/lipids on the surfaces of pathogens.
IL - 12
Inflammatory cytokine that activates NK cells which then produces IFN - gamma
which then activate macrophages.
Function of a TCR.
a. used only to recognize antigens
b. TCR membrane bound glycoprotein: recognize cell-to-cell contact.
Which complement receptors can recognize C3b?
CR 1 - CR 4
For expression of the TCR at the cell surface what is needed?
(list all proteins and the name given to all the proteins and TCR when on the
surface)
- needs the CD3 complex (Chr 11, homologous CD3 gamma, CD3 delta, & CD3
Epsilon)
- needs a zeta chain
Which Professional Antigen Presenting Cell (Professional - APC) is strong enough
to activate a CD8 T cell from a naive state?
Dendritic cells
What is a TCR complex?
a. all 8 polypeptides
b. aB chains from core; stable association w/4 invariant membrane proteins
c. z chain and CD3 complex interact w/intracellular signaling transduction.
i. lack of CD3δ in CD3ε = low expression and impaired signal transduction
C3 convertase of the Alternative Pathway
C3bBb
Function of a T cell receptor (TCR); TCR complex.
Function of a TCR:
- is to recognize MHC bound Ag's.
PCB 3233
, PCB 3233
- used only to recognize antigens (not effectors themselves.
TCR Complex:
- is the CD3 complex plus zeta chains.
- 2 transmembrane zeta chains which interact with intracellular signaling
molecules.
When will NK cells make interferon gamma?
When they are activated by IL-12 (inflammatory cytokine)
TCR antigen binding sites
a and b of the variable region
What is the CD 3 complex.
- a complex of proteins used to express the TCR.
- Encoded by closely-linked genes on human chromosome 11, homologous.
- Chromosome 11, homologous CD3γ, CD3δ, and CD3ε make it up.
- needed not only for signaling but high expression.
Explain the activation of macrophage feedback loop
NK cells become activated by IL- 12, they produce interferon gamma, IFN-
gamma activates macrophages, macrophages secrete IL-12 (+ other cytokines)
Describe the chains in a TCR?
V region followed by a C region followed by a membrane anchoring domain
TCR diversity
a. generated by gene rearrangement
b. prior to antigen stimulation: gene rearrangement = V region
c. post to antigen stimulation: genes encoding TCR remain unchanged
Where is the most variable region of the TCR?
V-alpha and V- beta
T-cell receptor antigen-binding sites, how many per TCR and number of CDR's
per receptor; T cell receptor diversity and where are most of the differences
concentrated?
Quantity:
- 1 antigen-binding site per TCR, and 6 CDR's per receptor (3 per chain).
PCB 3233
PCB 3233 - Immunology Exam 3 with
Correct Answers 2026 Update
Helper T cells associate with which class of MHC molecules?
MHC Class 2 (extracellular infection)
BCR (B cell receptor) and TCR (T cell receptor), how are they created and where
in the body are they created?
As a result of Gene Arrangement (VDJ Somatic Recombination).
- BCR: produced in Bone Marrow
- TCR: produced in Thymus
Interferon function
Viral fighting, they activate NK cells which then tell our infected cells to die by
apoptosis.
BCR and TCR how are they created?
somatic recombination - gene rearrangement = sequence variability in V regions
(bone marrow vs. thymus)
What process creates the variable region domain for both TCRs and BCRs?
Somatic Recombination
Structure of immunoglobulin and the T cell receptor (TCR)?
Ig:
- Ig = Heavy and light chains, Fab and Fc regions, 4 polypeptide chains, secreted.
TCR:
- (alpha) chain and (beta) chain each with variability and constant region.
- TCR = α and β chains, 2 polypeptide chains, CD3 complex (4 proteins for
signaling), 2 zeta chains, transmembrane.
Each chain has a variable and a constant region
What the different types IFN-1?
Alpha and Beta
PCB 3233
,PCB 3233
structure of immunoglobulin and the TCR
a. BCR: 4 polypeptide chain with a and b for signalling on the surface of a B cell
b. Domain structure of TCR is similar to lg
c. TCR: 2 polypeptide, CD3 complex (4 proteins for signaling), and 2 zeta chains
d. each chain has variable region and constant region
What are the differences and similarities between CD8 T Cells and NK cells?
The both have the same cytotoxic granules, NK cells are activated faster,
because they come out of the bone marrow "ready to go". CD8 T cells recognizes
MHC Class 1 + peptide (antigen) on a pathogen, while NK cells recognize normal
MHC Class 1 molecules on the surface of our cells and activating ligands that
infected cells put up on their surface.
The T cell receptor (TCR) type of antigen vs. Ig (BCR) type of antigen?
a) TCR
TCR:
- bind to peptide antigens which are derived from the pathogen's proteins.
- It requires presentation by MHC molecules.
- Cells bind one type of antigen which must be presented to them on the surface
of another human cell.
2 types of activating ligands
MIC - A and MIC - B, they bind to activating receptors on activating NK cells
The TCR type of antigen vs. lg type of antigen.
a. TCR only found on the surface of their t cells; multipoint attachement;
multiple copies of TCR bind to multiple copies of antigen (MHC complex on
opposing cell)
b. BCR can be secreted in the form of an antibody; bind epitopes on intact
molecules
Type 2 interferon
Also know as IFN- gamma, activates macrophages
The T cell receptor (TCR) type of antigen vs. Ig (BCR) type of antigen?
b) BCR
PCB 3233
,PCB 3233
BCR:
- bind intact molecules and DO NOT require presentation.
- bind to proteins/carbohydrates/lipids on the surfaces of pathogens.
IL - 12
Inflammatory cytokine that activates NK cells which then produces IFN - gamma
which then activate macrophages.
Function of a TCR.
a. used only to recognize antigens
b. TCR membrane bound glycoprotein: recognize cell-to-cell contact.
Which complement receptors can recognize C3b?
CR 1 - CR 4
For expression of the TCR at the cell surface what is needed?
(list all proteins and the name given to all the proteins and TCR when on the
surface)
- needs the CD3 complex (Chr 11, homologous CD3 gamma, CD3 delta, & CD3
Epsilon)
- needs a zeta chain
Which Professional Antigen Presenting Cell (Professional - APC) is strong enough
to activate a CD8 T cell from a naive state?
Dendritic cells
What is a TCR complex?
a. all 8 polypeptides
b. aB chains from core; stable association w/4 invariant membrane proteins
c. z chain and CD3 complex interact w/intracellular signaling transduction.
i. lack of CD3δ in CD3ε = low expression and impaired signal transduction
C3 convertase of the Alternative Pathway
C3bBb
Function of a T cell receptor (TCR); TCR complex.
Function of a TCR:
- is to recognize MHC bound Ag's.
PCB 3233
, PCB 3233
- used only to recognize antigens (not effectors themselves.
TCR Complex:
- is the CD3 complex plus zeta chains.
- 2 transmembrane zeta chains which interact with intracellular signaling
molecules.
When will NK cells make interferon gamma?
When they are activated by IL-12 (inflammatory cytokine)
TCR antigen binding sites
a and b of the variable region
What is the CD 3 complex.
- a complex of proteins used to express the TCR.
- Encoded by closely-linked genes on human chromosome 11, homologous.
- Chromosome 11, homologous CD3γ, CD3δ, and CD3ε make it up.
- needed not only for signaling but high expression.
Explain the activation of macrophage feedback loop
NK cells become activated by IL- 12, they produce interferon gamma, IFN-
gamma activates macrophages, macrophages secrete IL-12 (+ other cytokines)
Describe the chains in a TCR?
V region followed by a C region followed by a membrane anchoring domain
TCR diversity
a. generated by gene rearrangement
b. prior to antigen stimulation: gene rearrangement = V region
c. post to antigen stimulation: genes encoding TCR remain unchanged
Where is the most variable region of the TCR?
V-alpha and V- beta
T-cell receptor antigen-binding sites, how many per TCR and number of CDR's
per receptor; T cell receptor diversity and where are most of the differences
concentrated?
Quantity:
- 1 antigen-binding site per TCR, and 6 CDR's per receptor (3 per chain).
PCB 3233
