Bio 1040 Chapter 24

Cytotoxic T Cells Destroy

Infected Body Cells.

Neutralization of virus

using antibodies to prevent viruses from binding to receptors of host

The Cell-mediated Immune Response. (Dual defense)

Involves T Cell Lymphocytes that . . . Attack body cells infected with bacteria or viruses. Promote phagocytosis by other white blood cells. Stimulate B Cell Lymphocytes to produce antibodies.

The Humoral Immune Response (Dual defense)

Involves the production and secretion of free-floating antibodies into the bloodstream and lymphatic fluids by B Cell Lymphocytes.

The lymphatic system

Is comprised of lymph vessels & nodes, thymus, spleen, tonsils & adenoids. Functions closely with the circulatory system. Has several important functions: Lymphatic vessels of the small intestines (lacteals) absorb fats (lipoproteins) at the intestinal villi and transport them to the bloodstream. Lymphatic vessels absorb excess tissue fluid and return it to the bloodstream. Produce, maintain, & distribute of lymphocytes. Help defend the body against disease.

effector cells

Muscle cells or gland cells that carry out the body's response to stimuli.

Four Ways that Antibodies Mark Antigens for Elimination

Neutralization Agglutination Precipitation activation of the complement system

Vertebrate Innate Immunity Innate Immune Cells:

Neutrophils - "first-responder" phagocytes circulate freely in blood; are attracted to infection sites; squeeze between cells of capillary wall. Macrophages - "large" phagocytes that reside in, & wander through the interstitial fluids. Natural Killer Cells - attack cancer cells and virus-infected cells.

Helper T Cells

One type of T lymphocyte that activates B cells and other T lymphocytes

The Adaptive Immune Response Counters Specific Invaders

Only found in the Vertebrates. A second line of defense - when innate (non-specific) immune response fails to ward off a pathogen. Slower than innate defenses - i.e. normally takes 5 - 7 days to mount a response). Highly specific - involves the recognition of foreign cells, particles & molecules (i.e. "antigens") as "non-self" by the immune system. Recognition is mediated by antibodies. Can "remember" antigens or pathogens that have been encountered before. Involves B Cell & T Cell Lymphocytes. Often referred to as "acquired immunity

The Immune System Depends on

Our Molecular Fingerprints.

Apoptosis

Programmed cell death

Immunodeficiency Diseases (besides AIDS)

where an immune response is defective or absent.

Vertebrate Innate Immunity Barriers to Entry:

Skin - dead, keratinized cells form an impermeable barrier. Mucous membranes - form a sticky trap for microbes; ciliated cells sweep mucus & microbes into throat.

antibodies

Specialized proteins that aid in destroying infectious agents

The Primary & Secondary Responses Differ in

Speed, Strength & Duration

Cell-mediated Response -

T cells actively engage & destroy infected cells of the body.

Vertebrate Innate Immunity Inflammatory Response

The characteristic redness, swelling, pain and heat exhibited by a tissue when it is damaged by physical or chemical agents, or by infection.

Immune system is composed of

The lymphatic system (including lymph vessels & nodes; thymus, spleen, tonsils & adenoids). Bone marrow & a variety of white blood cells. Antibodies & complement proteins. A variety of signal molecules.

Antigen Presentation

The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell.

Clonal Selection (aka clonal recruitment)

The process whereby genetically unique (naïve or virgin) lymphocytes react with (recognize) their specific antigen for the very first time. Stimulates their mitotic proliferation.

Characteristics of Antigens: s.

They are molecules that elicit the adaptive immune response. They usually do not belong to the host animal. They are typically proteins or large polysaccharides on the surfaces of viruses or foreign cell

Cytotoxic T Cells Destroy Infected Body Cells

Virus protein fragments are tagged with ubiquitin. Ubiquitin facilitates secretion to cell surface. Cells are recognized by cytotoxic T cells.

T Cell Lymphocytes

Which type of cell engulfs other cells or pathogens?

Structure & Function of Antibodies

Y-shaped protein receptor molecules (aka Immunoglobins) produced by B cell lymphocytes. Comprised of four polypeptide chains: Two heavy + two light chains, each with variable & constant regions. Each recognizes or binds only one specific antigen. All function to mark antigens for destruction via phagocytes.

immune system

a system of organs, tissues, cells, and cell products that protect an organism from foreign & potentially harmful organisms, tissues or other substances.

Anaphylactic Shock

an immediate & severe allergic reaction that occurs when an allergen enters the bloodstream and affects the entire body

immunoglobins

antibodies

Cytotoxic T Cells

destroy pathogens and release chemicals called cytokines

Allergies -

fast, hypersensitive, overreactions of the immune system to normally harmless antigens.

Recruitment =

first antigen recognition - cell division is activated; many more cells are produced.

Allergic Reactions Occur In Two Stages: Stage 2 - Over Reaction

i.e. over-stimulation of the inflammatory response during a later exposure to the same antigen. Can be life-threatening or fatal.

Allergic Reactions Occur In Two Stages: Stage 1 - Sensitization

i.e. the very first exposure to an allergen - i.e. the antigen that elicits the allergen.

Active Immunity -

immunity that occurs when an individual produces his own supply of antibodies, either by exposure to a foreign entity or by immunization. e.g. Exposure to Chickenpox or Measles. e.g. Vaccination for Smallpox or Tetanus.

B cells

mature in marrow.

T cells

mature in thymus

Complement proteins enhance immune responses in three ways

1. Enhance Inflammation 2. Help Target Cells for Destruction 3. Form Membrane Attack Complexes

complement system

A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse extracellular pathogens.

Vertebrate Innate Immunity Complement System

A group of about 30 kinds of serum proteins that can act with (i.e. "complement") or help antibody & phagocyte defense mechanisms. Also help stimulate the inflammatory response.

Ubiquitin

A protein that attaches itself to faulty or misfolded proteins and thus targets them for destruction by proteasomes

antigen

A protein that, when introduced in the blood, triggers the production of an antibody

Adaptive Immunity

Aka acquired immunity. Involves a set of defenses developed for, and activated by specific pathogens or substances. Immune system "remembers" (or specifically recognizes) a previously encountered pathogen. Found only in the Vertebrates.

Innate Immunity

Aka non-specific, genetic, or natural immunity. Involves a set of defenses that are immediately active, and independent of previous encounters with a given pathogen or substance. Are the same, whether or not the pathogen has been previously encountered. Found in both vertebrates & invertebrates.

antibody

An antigen-binding immunoglobulin, produced by B cells, that functions as the effector in an immune response.

Antigenic Determinants -

specific regions on an antigen where antibodies bind. An antigen usually has several different determinants. The antigen-binding site of an antibody and an antigenic determinant have complementary shapes

agglutination

Antibody molecules may function by causing the An antibody-mediated immune response in which bacteria or viruses are clumped together, effectively neutralized, and opsonized.

Passive Immunity -

temporary immunity that occurs when an individual is given previously prepared antibodies to prevent a disease. e.g. Treatments for rabies & snakebites (anti-venom); unborn children & breastfed infants.

Vertebrate Innate ImmunityInterferons

Antiviral proteins produced by virus-infected cells that help to limit the cell-to-cell spread of viruses. "Interfere" with viral replication; & activate immune cells (e.g. natural killer cells and macrophages.

B cell lymphocytes

B cells have particular receptor sites on their surface for antigens to attach. When they encounter an antigen, they stimulate to become a plasma cell or a memory cell.

Humoral Response -

B cells release antibodies that tag (mark) antigens in body fluids for destruction.

Vertebrate Innate Immunity

Barriers to Entry: Innate Immune Cells: Interferons Complement System Inflammatory Response

lymph nodes

Bean-shaped filters that cluster along the lymphatic vessels of the body. They function as a cleanser of lymph as wells as a site of T and B cell activation

Autoimmune Diseases -

the immune system fails to distinguish between foreign antigens and "self" antigens; Cytotoxic T cells & antibodies attack the bodies own cells.

Clonal Selection Mobilizes what?

Defensive Forces Against Specific Antigens.

Lymphocytes Mount a

Dual Defense

Invertebrate Innate Immunity Includes

Exoskeleton - a hard impermeable chitinous "shell" that prevents the entry of foreign microbes. Low internal pH - that inhibits the growth of microbes. Lysozyme - an enzyme that degrades bacterial cell walls, causing them to lyse and die. Phagocytes - circulating immune cells that engulf and digest foreign substances. Recognition proteins - bind to microbes & trigger the release of antimicrobial peptides.

Antigen Presentation

Foreign cell, pathogen or particle is phagocytized by a macrophage. Particle is degraded into smaller antigen fragments that are attached to Self proteins. Self/non-self antigen complex is secreted to the cell surface for presentation to T cells.

Macrophages

Found within the lymph nodes, they are phagocytes that destroy bacteria, cancer cells, and other foreign matter in the lymphatic stream.

Memory cells

General term for lymphocytes that are responsible for immunological memory and protective immunity.