Cells of Adaptive Immunity

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Questions and Answers

What is the primary function of B lymphocytes?

  • Activating T cells
  • Transporting oxygen in the bloodstream
  • Producing antibodies (correct)
  • Destroying pathogens directly

Which statement accurately describes a difference between B cells and T cells?

  • T cells remain in the bone marrow to mature
  • T cells produce antibodies
  • B cells have B-cell receptors on their surface (correct)
  • B cells mature in the thymus

What are the two ways in which antibodies can be expressed by B cells?

  • Only as soluble proteins
  • Only as cell receptors
  • As cytokines and surface proteins
  • As soluble proteins and as cell receptors (correct)

What do B cells require to mount a strong immune response against most antigens?

<p>Activation signals from T Helper cells (A)</p> Signup and view all the answers

Which types of receptors do B cells possess?

<p>Major histocompatibility complex (MHC) 1 and 2 (C)</p> Signup and view all the answers

What occurs when a B cell encounters an antigen that matches its B-cell receptor?

<p>The B cell becomes activated and secretes antibodies (D)</p> Signup and view all the answers

Where do B cells primarily mature?

<p>In the red bone marrow (C)</p> Signup and view all the answers

How do B cells contribute to the humoral immune response?

<p>By secreting antibodies into body fluids (C)</p> Signup and view all the answers

Which of the following is true regarding B cell receptors?

<p>They are identical to the antibodies produced by B cells (C)</p> Signup and view all the answers

What triggers the activation of a B lymphocyte cell?

<p>Encountering an antigen that matches its B-cell receptor (D)</p> Signup and view all the answers

What type of receptors do B lymphocytes use to present antigens?

<p>MHC II receptors (B)</p> Signup and view all the answers

Which type of T cell is primarily responsible for activating other immune cells?

<p>T Helper cells (C)</p> Signup and view all the answers

What is the primary function of plasma cells after B cells differentiate?

<p>To secrete antibodies (C)</p> Signup and view all the answers

What distinction allows T Helper cells to recognize presented antigens?

<p>The presence of CD4 co-receptors and MHC II receptors (D)</p> Signup and view all the answers

Which cells specifically have MHC II receptors to present antigens?

<p>B cells, dendritic cells, and macrophages (D)</p> Signup and view all the answers

How do Cytotoxic T cells recognize and destroy infected self-cells?

<p>By recognizing foreign antigens on MHC I receptors (B)</p> Signup and view all the answers

Which of the following best describes the role of memory B cells?

<p>To survive long-term and respond to future infections (D)</p> Signup and view all the answers

What is the main difference between B cells and T cells in terms of antigen recognition?

<p>B cells can bind to free or soluble antigens, while T cells can only respond to presented antigens (C)</p> Signup and view all the answers

What defines the clonal selection process of B cells?

<p>The expansion of B cells that match specific antigens (D)</p> Signup and view all the answers

Match the following immune cell types with their functions:

<p>B cells = Produce antibodies T Helper cells = Activate immune responses Cytotoxic T cells = Destroy infected cells Memory B cells = Provide long-term immunity</p> Signup and view all the answers

Match the following types of MHC receptors with their associated T cell types:

<p>MHC I = Present antigens on all nucleated body cells MHC II = Present antigens on professional APCs</p> Signup and view all the answers

Match the following cytokine functions with the cell types that release them:

<p>B cells = Stimulate plasma cell differentiation T Helper cells = Reinforce B cell activation Plasma cells = Secrete antibodies Memory B cells = Persist for future immune responses</p> Signup and view all the answers

Match the following immune response characteristics with their descriptions:

<p>Clonal expansion = Production of identical immune cells Antigen presentation = Activation of T cells via MHC receptors Cytotoxic response = Direct attack on infected self-cells Humoral immunity = Antibody-mediated response</p> Signup and view all the answers

Match the following components of the immune system with their specific roles:

<p>Antibodies = Neutralize pathogens CD4 co-receptor = Facilitates T Helper cell recognition MHC molecules = Display antigens to T cells Granzymes = Induce apoptosis in targeted cells</p> Signup and view all the answers

Match the following types of immune cells with the specific receptors they possess:

<p>B cells = B-cell receptor (BCR) Cytotoxic T cells = CD8 co-receptor T Helper cells = CD4 co-receptor APCs = MHC II receptors</p> Signup and view all the answers

Match the following steps in the B cell activation process with their order:

<p>Antigen binding = B cell encounters antigen Endocytosis = B cell engulfs the antigen Antigen presentation = Displays peptide on MHC II T cell activation = Binds to T Helper cell</p> Signup and view all the answers

Match the following definitions with the terms related to B cell maturation:

<p>Plasma cells = Antibody factories Memory B cells = Long-lived immune cells Clonal selection = Selection of specific B cells for expansion Antigen specificity = Binding region on B cell receptor</p> Signup and view all the answers

Match the following features of T cells with their types:

<p>Cytotoxic T cells = Execute infected self-cells T Helper cells = Support other immune cells Naïve T cells = Prior to activation Memory T cells = Respond to previously encountered antigens</p> Signup and view all the answers

Match the following components related to B cells with their descriptions:

<p>B cell receptor (BCR) = Surface receptor that binds to specific pathogens Antibodies = Soluble form of BCR secreted by activated B cells MHC II receptors = Present antigens to T Helper cells MHC I receptors = Identify cells to the immune system</p> Signup and view all the answers

Match the following types of immune responses with their characteristics:

<p>Humoral immunity = Involves B cells and antibodies in body fluids Cell-mediated immunity = Involves T cells responding to infected cells Active immunity = Result from exposure to antigens Passive immunity = Result from antibodies received from another source</p> Signup and view all the answers

Match the following cells with their main functions:

<p>B cells = Produce antibodies T Helper cells = Activate other immune cells Plasma cells = Secrete large amounts of antibodies Memory B cells = Provide long-term immunity after exposure</p> Signup and view all the answers

Match the following stages of B cell activation with their descriptions:

<p>Antigen encounter = B cell binds to specific antigen via BCR Activation = B cell receives signals from T Helper cells Proliferation = B cell divides to produce clones Differentiation = B cells transform into plasma and memory cells</p> Signup and view all the answers

Match the following types of lymphocytes with their primary sites of maturation:

<p>B cells = Mature in bone marrow T cells = Mature in thymus Natural Killer (NK) cells = Mature in bone marrow Regulatory T cells = Mature in thymus</p> Signup and view all the answers

Match the following types of receptors with their roles in B cells:

<p>Immunoglobulin (Ig) receptor = Specific binding to antigens Major Histocompatibility Complex (MHC) II = Presenting antigens to T Helper cells Major Histocompatibility Complex (MHC) I = Identifying self-cells to the immune system B cell receptor (BCR) = Functional form of antibody on B cell surface</p> Signup and view all the answers

Match the following terms with their definitions regarding B cell function:

<p>Clonal selection = Process of selecting B cells that recognize specific antigens Affinity maturation = Process of increasing antibody binding strength Somatic hypermutation = Mutations in B cell receptors for improved affinity Isotype switching = Changing the class of antibodies produced</p> Signup and view all the answers

Match the stages of antibody response with their characteristics:

<p>Primary response = Initial antibody production after first exposure Secondary response = Faster and stronger response upon re-exposure Memory response = Long-lasting immunity by memory B cells Neutralization = Antibodies prevent pathogen from entering cells</p> Signup and view all the answers

Match the following functions with the respective B cell types:

<p>Plasma cells = Secrete antibodies into circulation Memory B cells = Persist in the body for long-term immunity Regulatory B cells = Help mediate immune responses Naive B cells = Unactivated B cells ready for antigen encounter</p> Signup and view all the answers

What process allows B cells to internalize antigens through their receptors?

<p>Receptor-mediated endocytosis (A)</p> Signup and view all the answers

What role do lymphokines play in B cell activation?

<p>They trigger B cell proliferation and differentiation. (A)</p> Signup and view all the answers

Which cells present antigens using MHC class I molecules?

<p>Infected cells (D)</p> Signup and view all the answers

Which type of T cell is responsible for directly destroying infected cells?

<p>Cytotoxic T cells (D)</p> Signup and view all the answers

What is the primary function of plasma cells once differentiated from B cells?

<p>Produce antibodies (C)</p> Signup and view all the answers

What best describes the adaptive immune system?

<p>It allows for a specific response to previously encountered pathogens. (B)</p> Signup and view all the answers

What triggers the activation of Helper T cells?

<p>Binding to MHC class II on macrophages (C)</p> Signup and view all the answers

What type of immunity do B cells contribute to?

<p>Humoral immunity (D)</p> Signup and view all the answers

Which protein is secreted by cytotoxic T cells to induce apoptosis in infected cells?

<p>Perforin (C)</p> Signup and view all the answers

What is the significance of memory T cells in the immune response?

<p>They enable a rapid response upon re-encountering pathogens. (A)</p> Signup and view all the answers

Match the following immune cells with their characteristics:

<p>B cells = Engage in receptor-mediated endocytosis Helper T cells (CD4+) = Release lymphokines to stimulate B cells Cytotoxic T cells (CD8+) = Induce apoptosis in infected cells Memory T cells = Provide rapid response to previously encountered antigens</p> Signup and view all the answers

Match the following immune responses with their characteristics:

<p>Humoral immunity = Involves B cells and antibody production Cell-mediated immunity = Involves T cells fighting infected cells Adaptive immunity = Specializes in recognizing specific pathogens Innate immunity = Provides immediate but non-specific response</p> Signup and view all the answers

Match the following types of T cells with their roles:

<p>Helper T cells (CD4+) = Activate B cells via MHC Class II Cytotoxic T cells (CD8+) = Detect and destroy virally infected cells Regulatory T cells = Suppress immune responses Memory T cells = Persist for long-term immune memory</p> Signup and view all the answers

Match the following processes with their descriptions:

<p>Receptor-mediated endocytosis = Engulfing of antigens by B cells Clonal selection = B cells proliferate in response to antigen Antibody production = Plasma cells generate specific antibodies Apoptosis = Programmed cell death of infected cells</p> Signup and view all the answers

Match the following antigen presentation processes with their associated MHC types:

<p>MHC Class I = Presents to Cytotoxic T cells MHC Class II = Presents to Helper T cells B cell antigen presentation = Utilizes MHC Class II for helper T cell activation Infected cell antigen presentation = Utilizes MHC Class I to display viral proteins</p> Signup and view all the answers

Match the following terms with their functions:

<p>Lymphokines = Stimulate B cell cloning Cytotoxins = Induce cell death in infected cells Antibodies = Neutralize pathogens in the humoral response Plasma cells = Produce antibodies specific to antigens</p> Signup and view all the answers

Match the following components of the immune system with their specific roles:

<p>B cell receptors = Bind to specific antigens MHC molecules = Present antigens to T cells Cytotoxic T cell receptors = Recognize infected cells displaying MHC Class I Helper T cell receptors = Bind to antigens presented by MHC Class II</p> Signup and view all the answers

Match the following stages of the immune response with their descriptions:

<p>Activation of B cells = B cells encounter specific antigens Differentiation into plasma cells = B cells proliferate and change function Production of memory cells = Long-lasting immunity post-infection Destruction of infected cells = Cytotoxic T cells target and eliminate infected cells</p> Signup and view all the answers

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Study Notes

B Lymphocytes

  • B cells are responsible for producing antibodies.
  • Antibodies are expressed by B cells in two ways:
    • B cell receptor (BCR): sits on the surface of a B cell and has the same structure as an antibody.
    • Secreted antibodies: identical to the BCR but in soluble form, released into body fluids.
  • Activated B cells release free soluble antibodies that bind specifically to the pathogen triggering the immune response.
  • B cells need activation signals from T Helper cells for a strong immune response.
  • B cells have three main types of receptors:
    • BCR (Ig receptor): unique and binds to a specific pathogen (antigen).
    • MHC 2: presents antigen to T Helper cells.
    • MHC 1: identifies the cell to the immune system.
  • Activation of a B cell occurs when it encounters and binds to an antigen matching its BCR.
  • The activated B cell presents pieces of the antigen on its MHC 2 receptor to a T Helper cell with a matching receptor.
  • T Helper cells and B cells release cytokines, activating each other to launch an immune response.
  • The B cell divides and differentiates into memory B cells and plasma cells.
  • Plasma cells: secrete thousands of antibodies per second, providing a soluble form of the BCR antibody.
  • Memory B cells: remain in the body for long periods ensuring a rapid response upon re-exposure to the same pathogen.

Clonal Selection

  • Clonal expansion: only B cells with matching antigen specificity are selected to divide and make identical cells (clones).
  • These clones are equipped to fight the specific pathogen that triggered the response.
  • Two main cell types are produced:
    • Plasma cells: antibody factories.
    • Memory B cells: long-lived and ready to fight a returning pathogen.

T lymphocytes

  • T lymphocytes are involved in cell-mediated immunity.
  • T cells require antigen presentation through MHC receptors.
  • T cells do not secrete antibodies but carry out diverse functions depending on the cell type.
  • Two main categories of T cells: T Helpers and Cytotoxic T cells.

T Helpers

  • Called CD4+ cells due to the presence of the CD4 co-receptor, which recognizes MHC2 receptors.
  • Only APCs (Antigen Presenting Cells) have MHC2 receptors and can activate T Helper cells:
    • B Cells
    • Dendritic Cells
    • Macrophages
  • T Helper cells activate and recruit other immune cells to fight infections.

Cytotoxic T Cells

  • Called CD8+ cells due to having CD8 co-recepetors which recognize MHC1 receptors found on all nucleated cells.
  • Cytotoxic T cells destroy infected cells using granzymes (digestive enzymes) and perforins (create holes in cell membranes) to prevent infection spread.
  • Recognize infected "self" cells displaying foreign antigens on their MHC1 receptors.
  • Antigen presentation stimulates naïve CD8+ and CD4+ T cells to differentiate into cytotoxic CD8+ cells or Helper CD4+ cells.

Summary

  • B cells: Humoral immunity (antibody production)
  • T cells: Cell-mediated immunity (direct cell destruction and immune coordination)
  • Antigen presentation: T cells require antigen presented through MHC receptors, while B cells can bind directly to free antigen.
  • MHC receptors: MHC1 found on all nucleated cells, MHC2 found only on APCs.
  • T Helper cells: Activate other immune cells, crucial for coordinating the immune response.
  • Cytotoxic T cells: Kill infected or abnormal cells, contributing to eliminating pathogens and preventing the spread of infection.

Lymphocytes: B and T Cells

  • B cells and T cells are the primary cells of the adaptive immune response.
  • B cells are responsible for antibody production.
  • T cells have a variety of roles in cell-mediated immunity.
  • B cells mature in the bone marrow, while T cells mature in the thymus.
  • Both B and T cells circulate in the blood and lymph and reside in secondary lymphoid organs.

B Cells: Humoral Immunity

  • B cells have B cell receptors (BCRs) on their surface, which are structurally similar to antibodies.
  • BCRs bind to specific antigens, triggering B cell activation.
  • Activated B cells secrete antibodies, which are soluble forms of their BCRs.
  • Antibodies bind to pathogens in body fluids, neutralizing them.
  • B cells need activating signals from T helper cells for a strong response, except for some specific antigens.
  • B cells express MHC II receptors, allowing them to present antigens to T helper cells.
  • B cells also express MHC I receptors, found on all nucleated cells.

B Cell Activation and Clonal Selection

  • B cell encounters and binds to an antigen matching its BCR.
  • B cell engulfs, digests, and presents antigen on its MHC II receptor.
  • T helper cell with a matching TCR binds to the presented antigen.
  • T helper cell and B cell release cytokines, activating each other.
  • B cell divides and differentiates into:
    • Plasma cells, antibody factories secreting thousands of antibodies per second.
    • Memory B cells, long-lived cells that provide rapid response upon re-exposure to the antigen.

T cells: Cell-Mediated Immunity

  • T cells require antigen presentation via MHC receptors.
  • T helper cells (CD4+) recognize antigens presented by MHC II receptors on antigen-presenting cells (APCs):
    • B cells
    • Dendritic cells
    • Macrophages
  • T helper cells coordinate and activate other immune cells.
  • Cytotoxic T cells (CD8+) recognize antigens presented by MHC I receptors, found on all nucleated cells.
  • Cytotoxic T cells destroy infected cells using granzymes and perforins.

Difference between B and T cells

  • B cells can bind to free antigens in body fluids.
  • T cells only recognize antigens presented by MHC receptors on other cells.
  • B cells produce antibodies that neutralize pathogens.
  • T cells have various functions, including activating other immune cells and directly destroying infected cells.

B Cells

  • Originate from hematopoietic stem cells in the bone marrow.
  • Travel through the bloodstream to the spleen and lymph nodes.
  • Have B cell receptors on their surface that bind to antigens.
  • Antigens are small molecules found on the surface of pathogens.
  • When an antigen binds to a B cell receptor, the B cell engulfs it via receptor-mediated endocytosis.
  • B cells break down the antigen and display fragments on their surface using MHC class II.
  • Helper T cells recognize and bind to MHC class II on B cells, triggering the release of lymphokines.
  • Lymphokines cause B cell clones to be produced and differentiate into plasma cells.
  • Plasma cells produce antibodies specific to the original antigen.

T Cells

  • Originate from hematopoietic stem cells in the bone marrow.
  • Helper T cells (CD4 lymphocytes) bind to MHC class II on B cells.
  • Cytotoxic T cells (CD8 lymphocytes) recognize and destroy infected cells.
  • Infected cells display viral proteins on their surface through MHC class I.
  • Cytotoxic T cells have T cell receptors that recognize abnormal peptides on infected cell surfaces.
  • Cytotoxic T cells secrete cytotoxins like perforin or granulysin to initiate apoptosis in infected cells.
  • Cytotoxic T cells can also express Fas ligand to trigger apoptosis in infected cells.
  • Memory T cells provide a rapid response to previously encountered pathogens.

Adaptive Immunity

  • B and T cells are both components of the adaptive immune system.
  • The adaptive immune system provides a specific response to pathogens, enhancing the body's ability to fight off infections.

B Cells

  • Originate from hematopoietic stem cells in bone marrow and travel to organs like spleen and lymph nodes
  • Possess B cell receptors on their surface that bind to antigens, which are foreign molecules on pathogens or recognized as foreign by the body
  • Utilize receptor-mediated endocytosis to engulf antigens
  • Break down antigens and display fragments on their surface with MHC Class II molecules
  • This allows Helper T cells (CD4+) to recognize and bind to MHC Class II
  • Upon recognition, Helper T cells release lymphokines, stimulating B cell cloning and differentiation into plasma cells
  • Plasma cells produce antibodies specific to the original antigen

T Cells

  • Helper T cells (CD4+) bind to MHC Class II on B cells and release lymphokines
  • Cytotoxic T cells (CD8+) recognize viral proteins displayed on MHC Class I of infected cells
  • Infected cells present abnormal viral proteins on their surface
  • CD8+ T cells bind to these abnormal proteins
  • CD8+ T cells release cytotoxins (perforin or granulysin) or FAS ligand to induce apoptosis of infected cells
  • Memory T cells provide rapid response to previously encountered antigens

Adaptive Immunity

  • B and T cells are key components of adaptive immunity
  • Adaptive immunity specializes in recognizing and fighting specific pathogens
  • It provides long-term protection and memory against infections

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