IMM: BLOCK 2: LECTURE 5: RECEPTORS

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Questions and Answers

What is the main focus of Chapter 5 in the course material?

T Cell Mediated Immunity

Antigen Recognition by T cells (correct)

Development of T Lymphocytes

B Cell Development

Which of the following best describes the receptors produced by B-cells and T-cells?

They are identical for all members of a species.

They are pre-determined and fixed for each individual.

They do not undergo any genetic changes.

They are created through random somatic chromosomal rearrangements and mutations. (correct)

What aspect of the immune system is highlighted by the diversity of receptors?

The innate immune system has unlimited receptor diversity.

Adaptive immunity features specialized receptor diversity. (correct)

Somatic mutations decrease receptor diversity.

Receptor diversity is irrelevant for immune function.

Which chapters will be covered in the next module focused on B cells?

Chapters 4 and 6 Signup and view all the answers

What is the primary function of B-cell receptors (BCRs)?

To bind epitope and initiate signaling Signup and view all the answers

Which part of the immune system has a limited number of receptors that remain consistent across individuals?

Pattern recognition receptors of the innate immune system Signup and view all the answers

What is a key characteristic of the immune receptors mentioned?

They provide vast variability for recognizing unique epitopes. Signup and view all the answers

Which of the following components is associated with B-cell receptors?

Igα and Igβ heterodimers Signup and view all the answers

How do receptors of the adaptive immune system achieve diversity?

By somatic generation of receptors Signup and view all the answers

Which of the following is NOT an objective of the lecture?

Evaluate the effectiveness of vaccines. Signup and view all the answers

Which statement is true regarding T-cell receptors (TCRs)?

They use random gene combinations to develop specificity. Signup and view all the answers

What is the expected outcome of somatic chromosomal rearrangements in lymphocytes?

The generation of a diverse array of specific receptors. Signup and view all the answers

What initiates the intracellular signaling cascade upon BCR binding an epitope?

Specialized cytoplasmic tails of Igα and Igβ Signup and view all the answers

What is the main reason for the deletion of the δ-chain locus during TCR γ & δ locus rearrangement?

It is positioned within the α-chain locus. Signup and view all the answers

Which of the following best describes the organization of the TCR γ locus?

It has one set of V segments with two C segments. Signup and view all the answers

How many Cδ gene segments are present in the δ locus?

One Signup and view all the answers

Why is the study of a specific subset of T cells highlighted by Kristel Yee Mon, Ph.D.?

They may serve as a biomarker for patient outcomes post-infection. Signup and view all the answers

What challenge related to diversity in the field of immunology is mentioned in Kristel Yee Mon's statement?

A limited number of black immunologists in faculty positions. Signup and view all the answers

What type of cells do activated B cells differentiate into that secrete antibodies?

Plasma cells Signup and view all the answers

What is the primary function of antibodies?

To bind specifically to antigens Signup and view all the answers

What component is part of the T-cell receptor (TCR) complex that helps link TCR with intracellular signaling?

CD3 complex Signup and view all the answers

Which accessory molecule can serve as a coreceptor for the T-cell receptor?

CD4 or CD8 Signup and view all the answers

Which statement correctly describes the T-cell receptor (TCR)?

It is a heterodimer comprising αβ or γδ chains. Signup and view all the answers

What is the primary characteristic of the antibodies secreted by plasma cells?

They are soluble forms of BCR. Signup and view all the answers

What is an Fab fragment in the context of T-cell receptors?

A fragment of immunoglobulin that binds antigens. Signup and view all the answers

Which molecules are involved in recognizing antigens in T lymphocytes?

MHC molecules Signup and view all the answers

What is the role of the complementarity-determining regions (CDR) in T-cell receptors?

They determine the antigenic specificity of the TCR. Signup and view all the answers

Which statement best describes the relationship between the α and β chains of a T-cell receptor?

They each span the cell membrane. Signup and view all the answers

How is the diversity of T-cell receptors generated?

Through gene rearrangement during T-cell development. Signup and view all the answers

Which of the following components is NOT associated with the core T-cell receptor complex?

CD4 Signup and view all the answers

What type of protein interactions facilitate the association of the TCR with CD3 proteins?

Electrostatic interactions between charged amino acids. Signup and view all the answers

What are hypervariable regions in the context of T-cell receptors?

Regions with high diversity in amino acid sequence. Signup and view all the answers

Which type of T-cell receptor includes γ and δ chains?

γδ T-cell receptor Signup and view all the answers

During α-chain rearrangement, which gene segments are involved?

Vα and Jα segments. Signup and view all the answers

What is the functional significance of the T-cell receptor complex's composition?

It enables antigen presentation and signal transduction. Signup and view all the answers

Which part of the T-cell receptor is primarily responsible for binding to the pMHC molecule ligand?

Variable region Signup and view all the answers

What is the primary function of the CD3 proteins in relation to the TCR?

To aid in the signaling pathway after TCR activation. Signup and view all the answers

What types of antigenic specificity do T-cell receptors recognize?

Only peptide antigens presented by MHC. Signup and view all the answers

How do γδ T-cell receptors differ from αβ T-cell receptors?

They are composed of different variable domains. Signup and view all the answers

In T-cell receptor gene rearrangement, what does the D stand for in V, D, J segments?

Diversity Signup and view all the answers

Study Notes

Somatically Generated Receptors of the Adaptive Immune System

Receptors created in lymphocytes of an individual through random somatic chromosomal rearrangements and mutations
Vast array of receptors specific for molecular details found in unique epitopes

Cell Surface Receptor Diversity

Receptors of the innate immune system (PRRs and complement receptors) are limited in number and diversity
Somatically generated receptors of lymphocytes in the adaptive immune system use random combinations of genes

Immunoglobulins (Ig) & T-cell receptors (TCRs)

Antigen receptors of adaptive immunity

B -Cell Receptors

Cell surface bound monomeric immunoglobulin associated with disulfide-linked heterodimers called Igα & Igβ
BCR binds an epitope
Specialized cytoplasmic tails of Igα & Igβ activate an intracellular signaling cascade that leads to B-cell activation
Some activated B cells terminally differentiate into plasma cells that secrete immunoglobulins

T-Cell receptors (TCRs)

Heterodimers, consisting of either an αβ or a γδ chain pair
Always membrane bound and recognize antigen combined with MHC molecules
Associated with CD3 complex
CD3 complex links TCR to intracellular signaling molecules.
An accessory molecule (CD4 OR CD8) serves as a coreceptor for TCR *

The T-cell Receptor Resembles a Membrane-bound Fab Fragment of Immunoglobulin

Membrane-bound heterodimer composed of an α chain and a β chain
Extracellular portion of each chain contains two immunoglobulin-like domains:
- Constant (C) domain
- Variable (V) domain
The 3D structure formed by the 4 immunoglobulin-like domains of TCR resembles the antigen-binding Fab fragment of antibody

T-cell receptor diversity is generated by gene rearrangement.

DNA recombination assembles a V-region sequence for each chain
For α chain, rearrangement of a Vα gene segment and a Jα gene segment creates a functional exon encoding the V domain.
For β chain, rearrangement of a Vβ , a Dβ, & a Jβ gene segment creates functional V-domain exon.
The assembled genes are transcribed and spliced to produce mRNA encoding α & β chains.

Expression of the T-cell receptor on the T-cell surface requires association with additional proteins

α & β chains bind antigen and form core TCR
This core αβ heterodimer associates with CD3γ & CD3δ & CD3ε & the ζ chain
Transmembrane domains of α & β chains contain positively charged amino acids (+) that form strong electrostatic interactions with negatively charged amino acids (–) in transmembrane regions of CD3γ, δ, & ε chains.

There are two classes of T-cell receptor

αβ T-cell receptor and γδ T-cell receptor have similar structures but different functions

The Organization of the Human T-cell Receptor γ-chain and δ-chain loci

TCR γ & δ loci (like α & β loci) contain sets of variable (V), diversity (D), joining (J), & constant (C) gene segments
δ locus is located within α-chain locus on chromosome 14, between clusters of Vα & Jα gene segments
There are at least 3 Vδ gene segments, 3 Dδ gene segments, 3 Jδ gene segments, & 1 Cδ gene segment
Vδ segments are interspersed among Vα and other gene segments
This arrangement means that DNA rearrangement within α-chain locus results in deletion of δ-chain locus.
The γ locus (chromosome 7) resembles β locus, with 1 set of V segments & 2 C gene segments each with its own set of J segments.

Kristel Yee Mon, Ph.D.

Studying a rare subset of T cells that may be a biomarker for patient outcome after infection with SARS-CoV2
Studying chemically enhancing innate immune cell types to better prime anti-tumor T cell killer function as a prospective cancer immunotherapy agent.

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Description

Test your knowledge on the somatically generated receptors of the adaptive immune system. This quiz covers the diversity of immunoglobulins, T-cell receptors, and B-cell receptors, emphasizing the mechanisms behind their activation and function. Dive into the complexity of immune responses and receptor formations.