Microbiology Lecture 14: Specific Defenses
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Questions and Answers

What type of defense is characterized by the body’s ability to recognize and defend against distinct invaders?

  • Innate defenses
  • Specific defenses (correct)
  • Nonspecific defenses
  • Physical barriers

Which of the following is NOT considered a part of the first line of defense in immune response?

  • Phagocytosis (correct)
  • Skin
  • Microbial antagonism
  • Mucous membranes

What is a main characteristic of the specific immune response?

  • It is acquired over time. (correct)
  • It lacks memory functions.
  • It does not distinguish between types of pathogens.
  • It acts immediately upon pathogen exposure.

What role do lymphocytes play in the immune response?

<p>They are involved in the specific immune response. (D)</p> Signup and view all the answers

How does the immune system demonstrate memory functions?

<p>By recognizing and responding faster to familiar pathogens. (B)</p> Signup and view all the answers

What defines an epitope in the context of antigens?

<p>A defined region of a molecule with antigenic properties (D)</p> Signup and view all the answers

What role does the lymphatic system play in the immune response?

<p>It screens tissues for foreign antigens and helps maintain fluid balance. (B)</p> Signup and view all the answers

Which of the following is NOT a method by which antigens can enter the body?

<p>Through direct sunlight exposure (B)</p> Signup and view all the answers

Which components are included in the lymphatic system?

<p>Lymphoid cells, lymphatic vessels, and various organs (A)</p> Signup and view all the answers

Which of the following statements about antigens is true?

<p>Antigens can be proteins found in bacteria, fungi, and food particles. (D)</p> Signup and view all the answers

What is lymph primarily composed of?

<p>Fluid leaked from blood vessels (A)</p> Signup and view all the answers

Where do lymphocytes primarily mature?

<p>Thymus and red bone marrow (A)</p> Signup and view all the answers

What is the function of lymph nodes?

<p>House leukocytes that attack foreign antigens (C)</p> Signup and view all the answers

Which organ is involved in filtering bacteria and viruses from the blood?

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

What happens during clonal selection of lymphocytes?

<p>They divide upon activation by an antigen (B)</p> Signup and view all the answers

Which of the following structures helps trap foreign particles and microbes?

<p>Tonsils and MALT (A)</p> Signup and view all the answers

What type of cell is a lymphocyte?

<p>White blood cell (C)</p> Signup and view all the answers

What is the primary role of lymphatic vessels in the body?

<p>To collect lymph and return it to circulation (A)</p> Signup and view all the answers

What is the role of T helper cells (CD4) in the immune response?

<p>Recognize MHC/Ag complex and direct the immune response (B)</p> Signup and view all the answers

Which type of cell directly eliminates cancer and virus-infected cells?

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

Where are T cells produced and matured?

<p>Red bone marrow and thymus (D)</p> Signup and view all the answers

What triggers the cell-mediated immune response?

<p>Display of pathogen-derived antigens on host cell membranes (C)</p> Signup and view all the answers

What mechanism do T cells employ to eliminate antigen-presenting cells?

<p>Release of perforin and granzyme (C)</p> Signup and view all the answers

What is the significance of MHC recognition for T cells?

<p>It allows the immune system to remove foreign cells. (B)</p> Signup and view all the answers

Which component is NOT involved in the cell-mediated immune response?

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

What is the result of improper regulation of T cell responses?

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

What is the primary role of plasma B cells in the humoral immune response?

<p>To secrete large quantities of antibodies specific to an antigen (D)</p> Signup and view all the answers

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

<p>They display antibodies on their membranes without secreting them. (B)</p> Signup and view all the answers

What is the significance of clonal selection in the humoral immune response?

<p>It allows for the selection of B cells that will become plasma cells. (A)</p> Signup and view all the answers

What is the primary purpose of lymphocyte editing via clonal deletion?

<p>To eliminate self-reactive lymphocytes (C)</p> Signup and view all the answers

Antigen-presenting cells (APCs) are crucial for B cell activation because they do what?

<p>Display antigens on their surface to signal T-helper cells. (A)</p> Signup and view all the answers

Which cells are primarily responsible for synthesizing and secreting antibodies?

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

What triggers the activation of B cells during the humoral immune response?

<p>Signals from T-helper cells through interleukins. (B)</p> Signup and view all the answers

What is a key characteristic of the antibodies' structure?

<p>They are composed of light and heavy chains (B)</p> Signup and view all the answers

What is the main difference between plasma B cells and memory B cells?

<p>Plasma B cells produce antibodies immediately, while memory B cells are for future responses. (C)</p> Signup and view all the answers

Which process involves the immune system sourcing antigen-specific B cells for a stronger response?

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

Which class of antibody is primarily involved in mucosal immunity?

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

What process occurs during the maturation of B cells that contributes to heterogeneity?

<p>Randomization of variable region receptors (A)</p> Signup and view all the answers

What role do cytokines play in B cell activation?

<p>They signal B cells to proliferate and differentiate. (C)</p> Signup and view all the answers

Which interaction is primarily responsible for the binding of an antibody to its antigen?

<p>Hydrogen bonds and other attractions (D)</p> Signup and view all the answers

How do T cells recognize self-antigens during clonal deletion?

<p>By recognizing MHC class I molecules (D)</p> Signup and view all the answers

What type of immune response are antibodies primarily associated with?

<p>Humoral immune response (A)</p> Signup and view all the answers

Which of the following is NOT a class of antibodies?

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

What triggers the differentiation of activated B cells into memory cells?

<p>Exposure to antigens after initial activation (D)</p> Signup and view all the answers

Flashcards

Antigen

Any molecule or part of a molecule that triggers a specific immune response.

Epitope

A specific region on an antigen that is recognized by the immune system.

Lymphatic System

A network of vessels, organs, and cells that help the body fight infections and maintain fluid balance.

What do B cells produce?

B cells produce antibodies, which are proteins that bind to antigens and mark them for destruction.

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Humoral Immune Response

The immune response mediated by antibodies that circulate in the blood.

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Innate Defenses

Natural, inborn resistance to most pathogens. This is a general, non-specific defense mechanism that the body has from birth.

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Nonspecific Defenses

The first and second lines of defense. These are general defenses that don't target specific pathogens.

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Specific Defenses

The third line of defense. This involves a targeted immune response to specific pathogens, mediated by lymphocytes and antibodies.

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What's the difference between innate and specific defenses?

Innate defenses are general and present from birth, while specific defenses are acquired over time and target specific pathogens.

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What is the third line of defense?

The third line of defense is a specific immune response that relies on lymphocytes and antibodies to target and destroy specific pathogens. This response is acquired through exposure to pathogens and provides long-term immunity.

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Lymph

A fluid similar to blood plasma that originates from fluid leaking from blood vessels into surrounding tissues.

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Lymphoid Cells

A type of white blood cell, including T-cells and B-cells, responsible for immune responses. They develop from stem cells in the bone marrow.

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Lymphatic Vessels

A one-way system that collects lymph from tissues, transports it to lymph nodes, and returns it to the circulatory system.

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Lymph Nodes

Small, bean-shaped organs that filter lymph, house leukocytes (white blood cells), and initiate immune responses against foreign antigens.

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Spleen

An organ similar in function to lymph nodes, filtering bacteria, viruses, toxins, and other foreign matter from the blood.

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Tonsils and MALT

Lymphoid tissues located in the throat and other mucosal areas, physically trapping foreign particles and microbes.

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Clonal Deletion

A process in which lymphocytes that recognize self-antigens are eliminated, preventing autoimmune reactions.

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Clonal Selection

A process where a lymphocyte is activated by a specific antigen, leading to cell division and the production of memory cells for future responses.

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Complement Activation

A cascade of proteins that helps fight off pathogens. It enhances inflammation, attracts phagocytes, and directly lyses bacteria.

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Agglutination

Antibodies bind to multiple antigens on multiple pathogens, clumping them together. This helps the immune system remove them.

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Neutralization

Antibodies block the binding sites of pathogens, preventing them from attaching to host cells.

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Opsonization

Antibodies coat pathogens, making them easier for phagocytes to recognize and engulf.

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B Cell Activation

The process of a B cell encountering an antigen and becoming activated, leading to the production of antibodies.

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Plasma B Cells

Short-lived cells that produce and secrete large amounts of antibodies.

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Memory B Cells

Long-lived cells that remember a specific antigen. If the same pathogen is encountered again, they quickly trigger a faster and stronger immune response.

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T Helper Cells (CD4)

A type of T cell that recognizes MHC/Ag complexes presented by antigen-presenting cells (APCs). They direct the specific immune response by activating other immune cells.

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T Cytotoxic Cells (CD8)

A type of T cell that triggers apoptosis (programmed cell death) in cells displaying incorrect Ag/MHC complexes. They are activated by interleukin 2 produced by T helper cells.

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MHC (Major Histocompatibility Complex)

A group of genes that determine the body's immune response. MHC molecules present antigens to immune cells, allowing them to distinguish self from non-self.

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How do T cells mature?

T cells are produced in the red bone marrow and mature in the thymus.

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What is the role of MHC in T cell maturation?

T cells must be able to recognize MHC molecules during their maturation in the thymus. This allows the immune system to distinguish self from non-self and prevent autoimmune reactions.

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Cell-Mediated Immune Response

A type of immune response that involves T cells directly targeting and destroying infected or abnormal cells.

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What type of pathogens does the cell-mediated immune response target?

The cell-mediated immune response targets intracellular pathogens, particularly viruses. It's also effective against intracellular bacteria and abnormal body cells (cancer).

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How is the cell-mediated immune response regulated?

Careful regulation of the cell-mediated immune response prevents T cells from attacking the body's own cells (autoimmune reactions). This regulation involves additional 'safeguard' signals with an antigen-presenting cell.

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Autoantigens

Antigens derived from the body's own tissues that can trigger an autoimmune response.

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What is the purpose of lymphocyte editing?

Lymphocyte editing eliminates self-reactive lymphocytes to prevent autoimmune diseases. It ensures that the immune system only targets foreign invaders and does not attack the body's own tissues.

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What is the difference between B and T cell editing?

Both B and T cells undergo clonal deletion, but T cells also require recognition of MHC class I molecules.

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How do B cells develop?

B cells originate from stem cells in the bone marrow. Self-reactive B cells are normally inactivated.

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What's special about B cell receptors?

Each mature B cell has two matching receptors with variable regions that are randomized during maturation, allowing for a diverse repertoire of antibodies.

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What happens when a B cell is activated?

An activated B cell differentiates into plasma cells that secrete antibodies, and memory cells that remember the specific antigen.

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What is the role of antibodies?

Antibodies, also known as immunoglobulins (Ig), are soluble proteins that circulate in blood and lymph, binding to and neutralizing specific antigens.

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What are the different classes of antibodies?

There are five major classes of antibodies: IgA, IgD, IgE, IgG, and IgM. Each class has specific functions and roles in the immune response.

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How do antibodies bind to antigens?

Antibodies form strong, noncovalent interactions with antigens through complementary binding sites, involving hydrogen bonds and other attractions.

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Study Notes

Microbiology - Lecture 14: Specific Defense Mechanisms

  • Defense Mechanisms (Overview):
  • Innate defenses provide natural resistance to pathogens.
  • Nonspecific defenses include first line (skin, mucous membranes, microbial antagonism) and second line (phagocytosis, inflammation, fever, signaling molecules).
  • Specific defenses are the third line, involving lymphocytes and antibodies.

Third Line of Defense (Specific Immunity)

  • Specific Immunity:
  • The body's ability to recognize and defend against distinct invaders.
  • "Smart" system with memory for rapid response to subsequent encounters.
  • Acquired over time through exposure.
  • Includes antigens, the lymphatic system, B cells, antibodies, humoral immunity, and cell-mediated immunity.

Antigens

  • Antigens:
  • Any molecule or molecular fragment triggering a specific immune response.
  • Includes components of bacterial cell walls, capsules, pili, flagella, viral proteins, fungal components, and protozoan proteins.
  • Epitope is the region of a molecule with antigenic properties. A single molecule may have multiple epitopes.
  • Antigens can enter the body through various pathways such as breaks in the skin, mucous membranes, injections, or transplants.

Lymphatic System

  • Lymphatic System:
  • A network of organs, vessels, and cells that screen the body for foreign antigens.
  • Lymphatic vessels collect lymph from tissues and return it to the circulatory system.
  • Lymph nodes, spleen, and tonsils are key components.
  • Lymph is similar to blood plasma, formed from leaked blood fluid.

Lymphocytes (Overview)

  • Lymphocytes:
  • Arise and mature in red bone marrow (B cells) or thymus (T cells).
  • Primarily found in the spleen and lymph nodes, with a smaller percentage circulating in the blood.
  • Activated by a single matching antigen, leading to cell division and the formation of memory cells.

Lymphocyte Editing by Clonal Deletion

  • Clonal Deletion:
  • A critical process to eliminate lymphocytes that respond to self-molecules (autoantigens).
  • Ensures the immune system does not attack the body's own cells.

Characteristics of B Cells

  • B Cells:
  • Originate from stem cells in bone marrow.
  • Clonal deletion inactivates B cells that respond to self antigens.
  • Diverse range of B cells (heterogeneity).
  • Each B cell has two matching receptors.
  • Antigen binding is highly specific.
  • Activated B cells develop into plasma cells (antibody secretion) or memory cells (rapid response to subsequent encounters).

Antibodies (Immunoglobulins)

  • Antibodies:
  • Soluble proteins composed of polypeptide chains (held by covalent bonds).
  • Circulate in blood and lymph, binding to antigens for neutralization, opsonization, or complement activation.
  • Secreted by plasma cells (activated B cells).
  • Part of the humoral immune response.

Structure of Antibodies

  • Antibody Structure:
  • Four polypeptides (2 heavy, 2 light chains), connected by covalent bonds.
  • Y-shaped molecule with two antigen-binding sites.
  • Constant region (Fc region) determines class.
  • Variable region (arms) binds to specific antigens.

Classes of Antibodies

  • Antibody Classes:
  • Different classes of antibodies have various roles in the immune response (IgA, IgD, IgE, IgG, IgM).

Antibody Function

  • Antibody Function:
  • Form strong, non-covalent interactions with antigens.
  • Interactions involve complement activation, inflammation, agglutination, neutralization, and opsonization.

Humoral Immune Response

  • Humoral Immune Response:
  • Antibody-mediated response against exogenous pathogens.
  • Involves B cell activation, clonal selection, plasma cell differentiation, and antibody secretion.
  • Requires the help of T helper cells.

Cell-Mediated Immunity

  • Cell-Mediated Immunity:
  • Involves T cells that directly attack cells with abnormal antigens (virus-infected cells, cancer cells).

Type T Lymphocytes (T Cells)

  • T Cells:
  • Produced in bone marrow, mature in thymus.
  • Crucial for recognizing MHC (major histocompatibility complex) / antigen complexes.
  • Two main types: T helper cells (CD4) and cytotoxic T cells (CD8).

Cell-Mediated Immune Response

  • Cell-Mediated Immune Response:
  • T cells act directly against various antigens (intracellular pathogens and abnormal body cells).
  • Triggered when host cells display antigens on their membrane.
  • Leads to memory T cell formation for subsequent responses.

Regulation of Cell-Mediated Response

  • Regulation of Cell-Mediated Response:
  • Carefully regulated to prevent T cells from responding to autoantigens (self-antigens).
  • T cells need activation signals provided by antigen-presenting cells.
  • Apoptosis (programmed cell death) is crucial for regulating cell-mediated responses.

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MIC 205 Specific Defence Ch 16 S21 PDF

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Explore the mechanisms of specific defenses against pathogens in microbiology. This quiz covers innate and specific immunity, detailing the roles of lymphocytes and antibodies, and the function of antigens. Test your knowledge of how the body recognizes and responds to distinct invaders.

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