02 Adaptive Immunity System: T-Cell Development

Questions and Answers

What happens to small pre-B cells that bind strongly to a self-antigen?

They rearrange their DNA segments.

They develop into mature B cells.

They undergo apoptosis. (correct)

They signal to the bone marrow.

What is the role of the light chain rearrangement in pre-B cells?

It reduces the binding strength to self-antigens. (correct)

It initiates signaling to the bone marrow.

It increases the chances of apoptosis.

It allows pre-B cells to develop into pre-T cells.

Under what circumstance does a small pre-B cell become an immature B cell?

It must rearrange both chromosome light chains successfully.

It must not recognize any self-antigens. (correct)

It must have a self-reactive B cell receptor.

It must bind strongly to a foreign antigen.

What ultimately signals a pre-B cell to exit the bone marrow?

The presence of IgD constant regions. Signup and view all the answers

What is true about the antibodies produced by B cells using IgM and IgD constant regions?

They share the same antigen binding specificity. Signup and view all the answers

What process do pre-B cells undergo to generate a new B cell receptor if the original is self-reactive?

DNA splicing and rearrangement. Signup and view all the answers

What characterizes the development process of B cells in lymphoid organs?

It involves iterative attempts at receptor rearrangement. Signup and view all the answers

Which of the following statements is false regarding the alternation of B cell receptors?

IgD has a different antigen binding specificity than IgM. Signup and view all the answers

What is the primary function of the adaptive immune response?

To differentiate between various types of invaders Signup and view all the answers

What are the two main types of lymphocytes involved in the adaptive immune response?

B cells and T cells Signup and view all the answers

During lymphopoiesis, which type of lymphocyte is formed in the bone marrow?

B cell Signup and view all the answers

Which of the following best describes the role of mesenchymal stem cells in the bone marrow?

They support the development of lymphocytes through interactions Signup and view all the answers

What is the significance of immunologic memory in the adaptive immune response?

It allows for an immediate response to previously encountered pathogens Signup and view all the answers

What is the process by which hematopoietic stem cells develop into lymphocytes called?

Lymphopoiesis Signup and view all the answers

Which characteristic distinguishes the innate immune response from the adaptive immune response?

It is immediate and non-specific Signup and view all the answers

Where do T cells complete their maturation process?

Thymus Signup and view all the answers

Which statement accurately describes the role of Rag-1 and Rag-2 in B cell development?

They assist in splicing D and J segments during heavy chain rearrangement. Signup and view all the answers

What feature distinguishes the light chain from the heavy chain in B cell receptors?

The light chain comprises only V and J segments. Signup and view all the answers

During which stage of B cell development does allelic exclusion first occur?

Late pro-B cell stage Signup and view all the answers

Which component is integral for testing the functionality of the heavy chain in a large pre-B cell?

Surrogate light chain Signup and view all the answers

What happens to a B cell if it expresses a self-reactive receptor?

It may be killed off or undergo iterative rearrangements. Signup and view all the answers

What genetic components are mixed and matched to create unique B cell receptors?

V, D, and J segments Signup and view all the answers

Which chain is responsible for determining the type of antibody generated by a B cell?

Heavy chain Signup and view all the answers

Which two proteins make up the surrogate light chain?

VpreB and lambda 5 Signup and view all the answers

What is the consequence of a failed gene rearrangement during B cell maturation?

The cell dies. Signup and view all the answers

What does the term 'immature B cell' refer to in relation to receptor specificity?

It has yet to undergo selection for self-reactivity. Signup and view all the answers

Which part of the heavy chain is unique to each B cell receptor?

Variable region Signup and view all the answers

Which enzyme is essential for the rearrangement of genes in both the heavy and light chains of B cell receptors?

Rag-1 and Rag-2 Signup and view all the answers

How many V gene segments does an average person inherit for the heavy chain?

44 Signup and view all the answers

What is the role of the AIRE gene in B cell development?

It helps to eliminate self-reactive B cells. Signup and view all the answers

Study Notes

Immune System Overview

Immune system has two main branches: innate and adaptive responses.
Innate immune response is immediate, non-specific, and cannot differentiate between invaders.
Adaptive immune response is specific and relies on receptors that identify unique invader parts known as antigens.

Adaptive Immune Response

Takes days to weeks to activate, but establishes immunologic memory.
Key cells: lymphocytes (B and T cells), generated during lymphopoiesis.

Lymphopoiesis

Goals:
- Generate diverse lymphocyte population with unique antigen receptors.
- Eliminate self-reactive lymphocytes.
- Mature non-self-reactive lymphocytes in secondary lymphoid tissue.

Development of B and T Cells

Hematopoietic stem cells in bone marrow mature into common lymphoid progenitors, eventually becoming either B or T cells.
B cells mature in bone marrow, becoming plasma cells in lymph nodes/spleen.
T cells migrate to thymus to develop into mature T cells.

B Cell Development Process

B cell goes through six stages: common lymphoid progenitor → early pro-B cell → late pro-B cell → large pre-B cell → small pre-B cell → immature B cell.
Interaction with mesenchymal stem cells in bone marrow aids development by providing adhesion molecules and growth factors like interleukin 7.

B Cell Receptor Formation

B cell receptor (BCR) has heavy and light chains configured during development.
The antigen binding site is formed by V (variable), D (diversity), and J (joining) segments.
Each heavy chain has 1 V, 1 D, and 1 J segment, while light chains have only V and J segments.

Gene Rearrangement

Successful gene rearrangement is critical; failure at any stage results in cell death.
Enzymes Rag-1 and Rag-2 initiate the rearrangement of D and J segments, leading to the late pro-B cell stage.
V(D)J recombinase connects D-J to V segment, completing the antigen binding site for the heavy chain.

Testing Heavy Chain Functionality

Large pre-B cells test heavy chain by binding to a surrogate light chain (VpreB and lambda 5) at the cell surface.
If successful, a signal for proliferation is sent, leading to small pre-B cells, which will now rearrange light chains.

Light Chain Rearrangement

Small pre-B cells can create either kappa or lambda light chains; kappa light chains are rearranged first.
Iterative process; unsuccessful attempts result in either further attempts or cell death.
Self-reactive B receptors are prevented from entering circulation to avoid autoimmune disease.

AIRE and Self-Reactivity

Autoimmune regulator gene (AIRE) enables expression of self-antigens in lymphoid organs, allowing pre-B cells to be tested against body-wide antigens.
Strong binding to self-antigens leads to apoptosis; intermediate binding prompts rearrangement to reduce reactivity.

Final Stages of B Cell Maturation

Immature B cells must signal the bone marrow upon completing development.
B cells express a mu heavy chain, marking the first antibody constant region, IgM.
B cells undergo alternative splicing to express either IgM or IgD, both maintaining the same antigen-binding specificity.

Immature B Cells and Antibody Types

The presence of IgD acts as a signal for the bone marrow, indicating the B cell is ready to enter the bloodstream.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the fundamental differences between the innate and adaptive immune responses in this quiz. Understand how the immune system functions like a military defense mechanism, distinguishing between immediate reactions and highly specific responses to invaders. Test your knowledge on these two vital branches of immunology.