Chapter 31: Immunology Animal Defense Systems

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Chapter 31: Immunology

Animal Defense Systems

Key Terms:
Acquired Immune Deficiency Syndrome (AIDS): arises from depletion of Th cells and as a result of infection with HIV

Adaptive Immunity: a set of specific mechanisms that respond to specific pathogens; they develop slower that innate responses but are long lasting; recognizes specific antigens, responds to an enormous diversity of antigenic determinants, distinguishes self from non-self, and remembers the antigens it has encountered setting the organism for prolonged immunity; involves antibody proteins

Allergic reaction: a normally harmless nonself molecule binds to a mast cell causing the release of histamine and inflammation; the nonself molecule comes from the environment; triggers an inappropriately strong response to the nonself molecule

Antibodies: part of our body (not the pathogen); reacts to an antigen with antigenic determinants; proteins that bind specifically to substances identified by the immune system as nonself. The binding can inactive and destroy microorganisms and toxins, or tag substances as nonself cells so the immune system can catch them later

Antigen-presenting cell: a cell that ingests and digests an antigen and then exposes fragments of that antigen to the outside of the cell, bound to proteins in the cell’s plasma membrane; B cells?

Antigenic determinants: epitopes; body’s response to an antigen with the antibodies; allow antibodies to match up and attach to an antigen (shape specific).

Antigen: any substance that stimulates the production of an antibody in the body of a vertebrate

Autoimmune diseases: the immune system fails to distinguish between self and nonself and attacks tissues in the organisms own body

Autoimmunity: an immune response by an organism to its own cells

Cellular immune response: mediated by T cells; acquires specific receptors to respond to each antigen

Class I MHC: found on surfaces of most cells in mammals

Class II MHC: found on most immune system cells

Clonal Deletion: inactivation or destruction of lymphocyte clones that would produce immune rx against the animal’s own body; prevention of autoimmunity

Clonal Selection: accounts for the specificity and diversity of the adaptive immune response and for immunological memory

Compliment System: more than 20 different proteins in the blood; once this system has been activated, the proteins function in a characteristic sequence (cascade) with each protein activating the next step.

Constant Region: determine which of 5 classes the immunoglobulin belongs to (these classes differ in function and type of heavy chain.)

Cytokines: Soluble signaling proteins released by many cell types; bind to surface cell receptors and alter the behavior of target cells; can activate or inactivate B cells, macrophages, and T cells

Cytotoxic T (Tc) cells: recognize and kill virus-infected cells or mutated cells

Defensins: also made my mucus membranes, these are peptides of 18-45 aa; they contain hydrophobic domains and are toxic to many pathogens; they insert themselves into the plasma membrane of organisms and make the membranes freely permeable to water and solutes (way to kill invaders). Defensins also are produced within phagocytes to kill pathogens consumed by phagocytosis

Effector cells: B cells and T cells that attack an antigen, either by secreting antibodies that bind to the antigen or by releasing molecules that destroy any cell bearing the antigen

Histamine: increases the permeability of blood vessels to aid in inflammation; an amino acid derivative

Human immunodeficiency virus (HIV):

Humoral immune response: part of adaptive immunity; involves antibody production by B cells (activated by binding of the antigen and by stimulation from Th cells with the same specificity; they then form plasma cells); acquires specific receptors to respond to each antigen

Immunity: two possible mechanisms in the body; immunity is the ability to avoid disease when invaded by a pathogen

Immunoglobulin: made of tetramers of 4 polypeptides; there are 2 identical light chains, and 2 identical heavy chains, each with a constant region and a variable region; many protein possibilities result when B cell genomes undergo recombination events

Immunological memory: part of the clonal selection response; the capacity to more rapidly and massively respond to a second exposure to an antigen than occurred on first exposure

Inflammation: a response that activates cells to act against invading pathogens when tissue is damaged; consists of redness, swelling, and heat which can be painful

Innate Immunity: a set of nonspecific, inherited mechanisms that protect the body from many kinds of pathogens; first defense is skin barriers and toxic molecules that destroy invaders; second defense is phagocytes

Interferon: increase resistance of neighboring cells to infection esp from viruses; type of cytokines

Lymphocytes: WBC; includes B cells and T cells; part of adaptive immunity

Lysozyme: enzyme made by mucus membranes which cleaves the bonds in the cell walls of bacteria causing them to lyse (burst open)

Major Histocompatibility Complex (MHC): these genes encode membrane proteins that bind antigenic fragments and present them to the Th cells; 2 classes; important slef-identifying labels that play a role in coordinating interactions between lymphocytes and macrophages

Mast cells: release histamine, which increases the permeability of blood vessels to aid in inflammation; adhere to skin and organ linings to release chemical signals

Memory cells: long-lived lymphocytes produced after exposure to antigen. They persist in the body and are able to mount a rapid response to subsequent exposures to the antigen

Mucus: slippery secretion produced by the mucus membrane in various body cavities, which are exposed to the external environment; mucus traps microorganisms so they can be removed by the beating of cilia which move mucus and trapped debris out of the body

Natural killer cells: defense cells that circulate the body and work to eliminate invaders by identifying healthy body cells from infected ones; can initiate apoptosis in infected cells; these also kill off antigens that have been labeled as targets by antibodies

Pathogens: harmful organisms and viruses that can cause disease

Phagocytes: WBC; defense cells that circulate the body and work to eliminate invaders through phagocytosis

Plasma cells: formed from B cells; they synthesize and secrete specific antibodies

Primary immune response: the first response of the immune system to an antigen, involving recognition by lymphocytes and the production of effector cells (T and B cells) and memory cells

Prostaglandins: fatty acid derivatives that play roles in various responses like the initiation of inflammation in nearby tissues

Regulatory T-cells (tregs): inhibit the other types of T cells from mounting an immune response to self-antigens

Secondary immune response: a rapid and intense response to a second or subsequent exposure to an antigen; initiated by memory cells

Sepsis: generalized inflammation caused by bacterial infection; can cause a dangerous drop in blood pressure

T-cell receptors: integral membrane proteins on the surfaces of T cells; recognize and bind to nonself substances presented y MHC proteins on the surface of other cells

T-helper cell (Th): direct cellular and humoral immune responses

Tumor necrosis factor: a cytokine protein that kills target cells and activates immune cells

Vaccination: injection of a virus or bacteria or their proteins into the body to induce immunity; the injected material is usually attenuated (weakened) before injection and is called a vaccine

Variable region: determines the specificity of an immunoglobulin

White Blood cells: specialized for various functions in the immune system; 2 major types: lymphocytes and phagocytes; aka leukocyte


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