B Cell Signal Transduction and Activation Quiz

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Questions and Answers

What is the minimum number of antigen molecules required to bind to adjacent membrane Ig molecules to induce signaling in B cells?

3 or more

4 or more

2 or more (correct)

What is the result of tyrosine phosphorylation of ITAMs in Igα and Igβ?

Recruitment and activation of molecules, mainly enzymes (correct)

Degradation of B cell receptors

Inhibition of signaling cascades

Inhibition of transcription factors

What is the consequence of B cell activation by antigens on B cell interaction with helper T lymphocytes?

Induces apoptosis of B cells

Prepares B cells to interact with helper T lymphocytes (correct)

Prevents interaction with helper T lymphocytes

Activates cytotoxic T cells

What is the outcome of Ig-mediated B cell activation on B cell proliferation?

Initiates B cell proliferation Signup and view all the answers

What is the consequence of B cell activation on IgM synthesis?

Initiates IgM synthesis Signup and view all the answers

What is the cellular component involved in the transduction of signals in B cells?

Ig alpha and Ig beta Signup and view all the answers

What is the main function of class II MHC molecules in B lymphocytes?

Present peptides derived from antigens Signup and view all the answers

Which chemokine receptor is most likely to be decreased in follicular helper T cells?

CXCR5 Signup and view all the answers

What is the role of CD40 ligand (CD40L) in the interaction between helper T cells and B lymphocytes?

Induces B cell proliferation Signup and view all the answers

What is a consequence of B cell proliferation induced by helper T cells?

Production and secretion of antibodies Signup and view all the answers

Which of the following is a critical step in the mechanisms of helper T cell-mediated B lymphocyte activation?

CD40L binding to CD40 Signup and view all the answers

How do cytokines affect B cell cytokine receptors in helper T cell-mediated B lymphocyte activation?

Stimulate B cell proliferation Signup and view all the answers

What is a key characteristic of antigens that induce the early phase of humoral immune response?

They are multivalent Signup and view all the answers

Which of the following is NOT a step in the process of B lymphocytes preparing for interaction with helper T cells?

Displaying peptides bound to MHCI molecules for helper T cell recognition Signup and view all the answers

What is a functional consequence of Ig-mediated B cell activation?

Increase in expression of costimulators such as B7 Signup and view all the answers

What initiates the process of B cell proliferation and IgM secretion?

Activation of B cells by antigens Signup and view all the answers

Which statement best describes the helper T cell dependent antibody response?

It requires activation of B cells by antigens Signup and view all the answers

What is a consequence of increasing the expression of receptors for chemokines produced in lymphoid follicles?

Increased B cell migration out of lymphoid follicles Signup and view all the answers

Study Notes

B Cell Proliferation and Differentiation

Antigen receptor-mediated signal transduction in B cells occurs when antigens induce clustering of membrane Ig receptors, triggering signals that activate B lymphocytes.
Cross-linking of membrane Ig receptors is required, which involves 2 or more antigen molecules or repeating epitopes of an antigen molecule binding to adjacent membrane Ig molecules of a B cell.

Antigen Receptor-Mediated Signal Transduction

The B cell receptor complex (BCR) consists of membrane immunoglobulin (IgM or IgD) and Ig alpha and Ig beta.
Ig alpha and Ig beta contain ITAM (immunoreceptors tyrosine-based activation motifs) tyrosines, which are phosphorylated by tyrosine kinases associated with the BCR complex.
Phosphorylated proteins recruit and activate molecules, mainly enzymes, that initiate signaling cascades that activate transcription factors.

Effects of B Cell Activation by Antigens

B cell activation by antigens initiates proliferation and differentiation of B cells.
It prepares B cells to interact with helper T lymphocytes if the antigen is a protein.
B cell activation leads to clonal expansion, IgM synthesis, and secretion.

B Cell Activation by Antigens

High-affinity membrane Ig receptors of B cells specifically bind and internalize an antigen through receptor-mediated endocytosis.
The antigen is delivered to endosomal vesicles and lysosomes, where it is processed into peptides.
Peptides bind to class II MHC molecules, leading to antigen processing and presentation.

Helper T Cell-Mediated Activation of B Lymphocytes

Helper T cells recognize peptide antigens presented by B cells on the B cells.
Activated helper T cells express CD40 ligand (CD40L) and secrete cytokines, which bind to their receptors on the same B cells and activate the B cells.
CD40L binds to CD40 on B lymphocytes, leading to B cell proliferation and production and secretion of antibodies.
Cytokines bind to B cell cytokine receptors, stimulating B cell proliferation and Ig production.

Mechanisms of Helper T Cell-Mediated Activation of B Lymphocytes

Helper T cell signals stimulate heavy chain isotype switching, induce the early phase of humoral immune response, and occur especially in polysaccharide and T-independent antigens.
Protein antigens need to induce signals in B lymphocytes that enhance their ability to interact with helper T lymphocytes.
B cells migrate out of lymphoid follicles and towards the T cell zones of lymphoid organs, allowing for interaction with helper T cells.

Functional Consequences of Ig-Mediated B Cell Activation

Ig-mediated B cell activation leads to increased expression of costimulators such as B7.
It increases expression of CKRs and decreases expression of receptors for chemokines produced in lymphoid follicles.
B cell activation prepares B cells for interaction with helper T cells.

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Description

Test your knowledge on B cell proliferation, differentiation, and antigen receptor-mediated signal transduction. Learn how antigens induce signaling in B cells and the role of receptor cross-linking in activating B lymphocytes.