B Lymphocyte and Antibody Response

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Questions and Answers

What is the role of helper T cells in the activation of B cells?

  • They directly activate B cells by releasing cytokines.
  • They directly activate B cells by binding to their MHC class II molecules.
  • They phagocytize and process antigens to present them to B cells.
  • They provide confirmation to B cells, leading to their activation and differentiation. (correct)

Which of the following describes the process of antigen presentation by B cells?

  • B cells internalize the antigen, break it down, and display fragments on MHC class I molecules.
  • B cells present intact antigens on their surface for recognition by T cells.
  • B cells internalize the antigen, break it down, and display fragments on MHC class II molecules. (correct)
  • B cells do not present antigens, they only recognize and bind to them.

What is the function of the T-cell receptor (TCR)?

  • It binds to the antigen on the B cell's surface.
  • It recognizes and binds to specific peptide fragments presented by MHC class II molecules. (correct)
  • It activates B cells by releasing cytokines.
  • It binds to the MHC class II molecules on the B cell's surface.

How does the antigen binding to a B-cell receptor lead to the activation of a B cell?

<p>The antigen binding initiates a signal cascade leading to changes in gene expression and differentiation. (B)</p> Signup and view all the answers

What is the difference between primary and secondary immune responses?

<p>The secondary response is much faster and stronger due to the presence of memory cells. (C)</p> Signup and view all the answers

Which of the following is NOT a direct consequence of antigen binding to a B-cell receptor?

<p>Direct activation of the B cell to produce antibodies. (C)</p> Signup and view all the answers

Which of the following cells are responsible for phagocytizing and processing antigens?

<p>Macrophages (B)</p> Signup and view all the answers

How do cytotoxic T cells contribute to the immune response?

<p>They directly kill infected cells by releasing cytotoxic substances. (A)</p> Signup and view all the answers

What is the essential function of macrophages in the immune response?

<p>To present antigens to other immune cells (A)</p> Signup and view all the answers

What is the outcome of a B-cell encountering an antigen that it is unresponsive to?

<p>Tolerance to that antigen is established. (A)</p> Signup and view all the answers

What is the significance of the MHC (Major Histocompatibility Complex) in the context of the immune response?

<p>It plays a vital role in antigen presentation. (C)</p> Signup and view all the answers

What is the core function of B-cell activation?

<p>Generating an adaptive immune response specific to an antigen (B)</p> Signup and view all the answers

What is "affinity maturation" in the context of B-cell activation?

<p>The process of B-cells becoming more effective at binding to a specific antigen (B)</p> Signup and view all the answers

What is the main function of "class switching" in the context of B-cell activation?

<p>To generate different antibody classes with distinct functions (C)</p> Signup and view all the answers

What is the implication of B-cells exhibiting a higher binding affinity for an antigen during activation?

<p>The B-cell will be more likely to proliferate (A)</p> Signup and view all the answers

Why is the mechanism of B-cell unresponsiveness to self-antigens crucial for maintaining health?

<p>It prevents autoimmune diseases by avoiding attacks on the body's own tissues (C)</p> Signup and view all the answers

What is the primary function of dendritic cells in the immune response?

<p>To present antigens to T cells (B)</p> Signup and view all the answers

In which location do dendritic cells mature and acquire the ability to present antigens to naive T cells?

<p>Secondary lymphoid organs (B)</p> Signup and view all the answers

What is the role of IL-2 in T cell activation?

<p>Stimulating T cell growth (B)</p> Signup and view all the answers

How do cytotoxic T cells (Tc cells) induce apoptosis in infected cells?

<p>By releasing pre-formed cytokines (A)</p> Signup and view all the answers

Which type of MHC molecule is recognized by cytotoxic T cells?

<p>MHC class I (A)</p> Signup and view all the answers

What is the primary role of helper T cells (TH cells) in the immune response?

<p>Orchestrating the immune response (C)</p> Signup and view all the answers

What type of cells express MHC class II molecules?

<p>Only antigen-presenting cells (APCs) (D)</p> Signup and view all the answers

How do TH cells activate B cells?

<p>By releasing cytokines that stimulate B cell proliferation (C)</p> Signup and view all the answers

What is the role of TH cells in macrophage activation?

<p>To deliver cytokines that enhance macrophage's killing mechanisms (C)</p> Signup and view all the answers

What is the primary function of the thymus in T cell development?

<p>To provide a site for T cell maturation and selection (A)</p> Signup and view all the answers

What is the main difference between the functions of Tc cells and TH cells?

<p>Tc cells kill infected cells, while TH cells activate other immune cells. (D)</p> Signup and view all the answers

Which of the following is NOT a function of cytokines?

<p>Directly destroying pathogens (A)</p> Signup and view all the answers

Which of the following is a characteristic of T cell activation?

<p>The production of adhesion molecules enables T cell migration to the site of infection. (B)</p> Signup and view all the answers

What is the role of class switching in B cell activation?

<p>It allows B cells to produce different types of antibodies. (B)</p> Signup and view all the answers

What is the primary function of B memory cells?

<p>To provide a rapid response to subsequent infections with the same pathogen. (D)</p> Signup and view all the answers

Which of the following is NOT a cell type that can produce cytokines?

<p>Neurons (B)</p> Signup and view all the answers

Flashcards

B Lymphocytes

A type of white blood cell that produces antibodies.

Antibody Response

The process by which B lymphocytes produce antibodies after activation.

B cell Activation

The process where B cells become ready to produce antibodies, requiring antigen binding and helper T cells.

Antigen Presentation

When degraded antigen fragments are displayed on MHC class II molecules for helper T cells.

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Helper T Cells

A type of T cell that provides signals necessary for B cell activation.

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Primary Response

The initial immune response when an antigen is first encountered.

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Secondary Response

The immune response upon re-exposure to the same antigen, faster and stronger than primary.

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T-cell Receptor

A molecule on T cells that recognizes specific antigens presented by MHC molecules.

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Antigen-presenting cells (APC)

Cells like macrophages that present antigens to T-helper cells.

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Tolerance

Unresponsiveness to future exposure of an antigen due to prior recognition.

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MHC

Major Histocompatibility Complex, crucial for antigen presentation.

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Class switching

B-cells change the type of antibody they produce based on the immune response needs.

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Affinity maturation

Evolution of B cells to produce antibodies with higher affinity for an antigen.

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Proliferation

The rapid multiplication of cells, particularly B cells after activation.

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IgM and IgG

Types of antibodies; IgM is the first, IgG is most common in circulation.

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Immature dendritic cells

Found in peripheral tissues, gather materials via phagocytosis and pinocytosis.

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Mature dendritic cells

Travel to secondary lymphoid organs to present antigens to naïve T cells after maturation.

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Activation of T cells

T cells produce cytokines (like IL-2) and adhesion molecules upon activation.

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Tc (CD8) cells function

Induce apoptosis in infected or cancerous cells through lethal functions.

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MHC class I molecules

These molecules present protein fragments to circulating Tc cells for recognition.

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Cytokines in immunity

Produced by various cells, they signal and coordinate immune responses.

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TH (CD4) cells function

Orchestrate immune responses by recognizing antigens presented by MHC class II.

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APC and MHC class II

Antigen Presenting Cells present antigens on MHC class II for TH cell recognition.

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Macrophage activation

TH cells activate macrophages to enhance their destructive capabilities against microbes.

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Lymphocyte development

B cells develop in bone marrow and T cells in thymus, learning to recognize antigens.

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Naïve T cells

T cells before activation, awaiting signals from dendritic cells and APCs.

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Cytotoxic functions

Tc cells release cytokines to destroy target cells that are infected or cancerous.

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Helper role of TH cells

TH cells bind to B cells and activate them for an immune response.

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Peptide loading

Nucleated cells degrade proteins and load peptides into MHC class I molecules for display.

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Study Notes

B Lymphocyte and Antibody Response

  • Antigens bind to B cell receptors, triggering B cell response
  • Often, helper T cells (TH cells) are needed for B cell activation
  • Activated B cells divide and differentiate to produce antibodies
  • Antigens enter the body, are engulfed by macrophages, and processed
  • Macrophages present a portion of the antigen on their surface, acting as antigen-presenting cells (APCs)

B-Cell Activation

  • Antigen binds to a B cell receptor
  • B cell internalizes the antigen
  • Antigen is broken down into peptide fragments
  • Fragments are presented on the B cell surface via MHC class II molecules
  • Helper T cells (TH cells) recognize the presented fragments
  • Cytokines are released, initiating B cell proliferation
  • If no recognition, B cell remains unresponsive with tolerance to the antigen

Characteristics of Activated B Cells

  • Enhanced immune response - including affinity maturation
  • Class switching: initial IgM secretion, then other antibody classes (e.g., IgG)
  • Memory cell formation: some B cells become long-lived memory cells, allowing a faster secondary response upon re-exposure to the antigen

Characteristics of Primary Response

  • Lag period (10-14 days): antibody detection in the blood is slow and low
  • The immune system is actively responding with initial B cell activation
  • Antibody concentration (titer) increases slowly
  • IgM is initially produced, followed by IgG production

Characteristics of Secondary Response

  • Faster response compared to primary response
  • Memory B cells quickly recognize the antigen
  • Large quantities of IgG are produced sooner than in the primary response
  • IgM is produced in smaller amounts and for a shorter period than IgG

T Lymphocytes Antigen Recognition and Response

  • Two main types of T cells: cytotoxic T cells and helper T cells
  • Cytotoxic T cells (Tc cells) destroy infected or cancerous cells
    • Recognize MHC class I (endogenous) antigens
  • Helper T cells (TH cells) activate B cells and macrophages
    • Recognize MHC class II (exogenous) antigens

Activation of T Cells

  • Dendritic cells are crucial in T cell activation
  • Immature dendritic cells in peripheral tissues collect materials
  • Dendritic cells travel to secondary lymphoid organs and mature
  • Mature dendritic cells present the antigen to T cells
    • This process stimulates T cell proliferation and effector function development

T Lymphocyte Antigen Recognition and Response

  • Cytokines produced by TH cells activate macrophages
  • This enhances macrophage's ability to destroy engulfed antigens

Classification

  • Cytokines are categorized based on their biological effects, including pro- and anti-inflammatory properties
  • Major categories include interleukins, interferons, and tumor necrosis factors

Lymphocyte Development

  • B and T cells develop the ability to recognize specific epitopes from pathogens
  • B cells mature in the bone marrow, T cells in the thymus

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