B Cell and T Cell Diversity Quiz

Questions and Answers

What is the primary mechanism by which B and T cells generate receptor diversity?

Random mutation of genes

Separate lineage for each antigen receptor

Clonal selection of immune cells

Combination of variable gene segments (correct)

How many protein-coding genes are present in the human genome as mentioned?

10,000

20,000 (correct)

1 million

5,000

Which segments compose the light chain of B cell antigen receptors?

Variable (V), Joining (J), and Transcription (T)

Variable (V), Joining (J), and Constant (C) (correct)

Constant (C), Alternative (A), and Variable (V)

Repetitive (R), Encoding (E), and Separator (S)

How many different V segments are available in the light-chain gene described?

40 Signup and view all the answers

What do the V and J segments together encode in the receptor chain?

The variable region Signup and view all the answers

What is the role of the recombinase enzyme complex during B cell development?

To link V and J gene segments and eliminate intervening DNA Signup and view all the answers

Why is the diversity of antigen-binding sites critical for the immune response?

It ensures B cells can recognize a wide array of antigens. Signup and view all the answers

What happens to the rearrangements made to the light-chain gene in B cells?

The rearrangements are permanent and passed to daughter cells. Signup and view all the answers

How many different combinations of light-chain gene segments can be created from the available segments?

200 Signup and view all the answers

Which statement accurately describes the final step after the rearrangement of genes in B cells?

Rearranged genes are translated to produce antigen receptors. Signup and view all the answers

What introduces additional variation into the antigen-binding specificities during VJ recombination?

The introduction of mutations. Signup and view all the answers

What is the estimated total number of antigen-binding combinations in the human population of B cells?

3.5 million Signup and view all the answers

How are the light-chain and heavy-chain genes described in terms of their rearrangement during B cell development?

Only one type of chain is rearranged actively at any time. Signup and view all the answers

Study Notes

B Cell and T Cell Diversity Generation

Each individual produces over 1 million unique B cell antigen receptors and 10 million unique T cell antigen receptors.
Human genome contains approximately 20,000 protein-coding genes, raising questions about the generation of receptor diversity.
Immune system creates a vast array of antigen receptors by combining different genetic elements, similar to selecting from multiple options (e.g., sizes and colors of a cell phone).

Immunoglobulin (Ig) Gene Structure

Immunoglobulin genes encode essential components for B cell antigen receptors and secreted antibodies (immunoglobulins).
Ig light chain is formed from three gene segments: variable (V), joining (J), and constant (C).
The V and J segments determine the variable region of the receptor, while the C segment specifies the constant region.

Specifics of Light-Chain Gene

The light-chain gene consists of:
- One constant (C) segment
- 40 different variable (V) segments
- 5 different joining (J) segments
This structural organization enables a diverse combination of V and J segments, contributing to the variability of antigen receptors in B and T cells.

Mechanism of Diversity

The diversity in antigen receptors results from the random selection and recombination of the V, J, and C gene segments during B and T cell development.
This combinatorial approach allows for a high degree of variability and specificity in immune responses, tailored to a wide array of pathogens.

Immunoglobulin Gene Diversity

Functional immunoglobulin (Ig) genes are constructed from segments that can be combined in 200 different combinations (40 V * 5 J * 1 C).
Heavy-chain gene combinations are even more diverse than light-chain combinations.
Rearrangement of DNA is necessary to create a functional Ig gene during B cell development.
Recombinase enzyme complex links one light-chain V gene segment to one J gene segment, removing the DNA between segments and forming a single exon.
Recombinase acts randomly, meaning any V gene segment can link with any J gene segment.
Only one allele of a light-chain gene and one allele of a heavy-chain gene undergo rearrangement in each cell.
The rearrangements of genes are permanent, inherited by daughter cells during lymphocyte division.
After rearrangement, the genes are transcribed and processed, leading to the translation and assembly of light and heavy chains to form antigen receptors.
Each pair of randomly rearranged heavy and light chains results in distinct antigen-binding sites.
The total number of antigen-binding combinations in the human B cell population is approximately 3.5 million (3.5 * 10^6).
Mutations accrued during VJ recombination further increase the diversity of antigen-binding specificities.

Description

Explore the fascinating mechanisms behind the generation of B cell and T cell antigen receptors. This quiz will cover how the human immune system creates a vast diversity of receptors through genetic combinations, despite the limited number of protein-coding genes. Test your understanding of this essential aspect of immunology!