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Human Physiology 2 > Ch. Ten: Body Defences > Flashcards

Ch. Ten: Body Defences Flashcards

1
Q

Immune Systen Activities

A
  • defends against invading pathogens
  • removes “worn out” cells and tissue damage by trauma
  • identifies and destroys abnormal or mutant cells that have originated in the body
  • mounts inappropriate immune responses that lead either to allergies or to autoimmune diseases
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2
Q

Major Targets of Immune System

A
  • bacteria: non-nucleated, single-celled microorganisms; primarily cause tissue damage and cause disease by releasing enzymes or toxins
  • viruses: consists of either DNA or RNA enclosed by a protein coat; cannot carry out metabolism or reproduce without invading a host cell
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3
Q

Defenses at Body Surfaces

A
  • first line of defense against microbes are the barriers: surfaces exposed to the external enviro and their various antimicrobial secretions
  • skin: physical; skin and salivary glands produce antimicrobial chemicals
  • mucous membranes: sticky secretions
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4
Q

Denfenses of Digestive System

A
  • saliva in mouth help combat bacteria:
  • “friendly” bacteria in mouth convert nitrate into nitrite which is swallowed
  • nitrite is converted to nitric oxide in stomach which is toxic to bacteria
  • strong gastric juice kills other bacteria
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5
Q

Leukocytes (Review)

A
  • neutrophils: highly mobile phagocytes that engulf and destroy
  • eosinophils: secrete chemicals that fight parasites; involved in allergic reactions
  • basophils: release histamine and heparin; involved in allergic reactions
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6
Q

Innate Immune System

A
  • nonspecific
  • responses work immediately when body is exposed to threatening agent
  • non-selectively defend against foreign invaders: recognize general molecular properties marking the invader as foreign
    ex. sugars or lipids on microbial walls
  • rapid but imited responses
  • neutrophils, macrophages, several plasma proteins are important in innate defense
  • first line of (internal) defense
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7
Q

Adaptive or Acquired Immune System

A
  • specifically targets foreign material to which body has already been exposed
  • body has taken time to prepare to attack
  • ultimate weapon against most pathogens
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8
Q

Adaptive Response includes:

A
  • antibody-mediated immunity: B-cells production of antibodies
  • cell-mediated immunity: involved production of activated T lymphocytes; directly attack unwanted cells
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9
Q

Innate Defenses include:

A
  • inflammation
  • complement system: plasma proteins attack cell membranes
  • interferon: viral infections
  • natural killer cells: lyse viral-infected and cancer cells
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10
Q

Innate: Inflammation

A
  • nonspecific response to tissue injury, foreign invasion
  • bring phagocytes and plasma proteins to invaded or injured area:
  • isolate, destroy, or inactivate the invaders, remove debris, prepare for subsequent healing and repair
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11
Q

Leukocyte Emigration From the Blood

A
  • chemotaxis: chemicals released initiate rolling (margination) and migration
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12
Q

Inflammation Summary

A
  • response is similar no matter what the triggering event
  • defense by resident tissue macrophages
  • localized vasodilation
  • increased capillary permability
  • localized edema
  • walling-off the inflamed area
  • emigration of leukocytes (Diapedesis)
  • leukocyte proliferation (neutrophils and monocytes)
  • marking of bacteria for destruction by opsonins
  • leukocytic destruction of bacteria
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13
Q

Innate Immunity Secreted Chemical

A
  • histamine: from mast cells; induces local vasodilation and increases capillary permeability
  • interleukin-1 and 6, TNF: from macrophages, fever, promote inflammation, enhances proliferation and differentiation of B and T lymphocytes
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14
Q

Phagocytosis

A
  • recognize certain carbohydrates or lipid on bacterial wall after contact:
  • can be aided by opsonins (“to prepare for eating”)
  • pus is a collection of phagocytotic cells, dead tissue
  • opsonins: not the name of a chemical! describes the action of some agents to help phagocytosis
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15
Q

Tissue Repair

A
  • can be perfect: cell division replaces lost cells with same kind of cells
  • non-regenerative tissues (nerve and muscle): lost cells are replaced with scar tissue
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16
Q

Complement System

A
  • nonspecific response
  • composed of plasma proteins: produced by liver and circulate in inactive form
  • primary mechanism: activated by antibodies to kill foreign cells (classical pathway)
  • alternative pathway: activated by exposure to carbohydrate chains present on surfaces of microorganisms
  • forms membrane attack complexes that punch holes in victim cells
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17
Q

Complement Proteins in inflammatory Process

A
  • acting as opsonins
  • promoting vasodilation and increased vascular permeability
  • stimulating release of histamine from mast cells
  • chemotaxins
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18
Q

Antiviral Effect of Interferon

A
  • transiently inhibits multiplication of viruses in most cells
  • triggers the production of virus-blocking enzymes by potential host cells- released nonspecifically from any cell infected by a virus
  • provides general, rapid defence until more specific but slower-responding immune mechanisms can begin
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19
Q

Natural Killer (NK) cells

A
  • naturally occurring lymphocyte-like cells
  • nonspecifically destroy virus-infected cells and cancer cells
  • mode of action: directly lyse cell membranes upon first exposure to these cells
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20
Q

Antibody-mediated (humoral immunity)

A
  • production of antibodies by activated B lymphocytes= plasma cells
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21
Q

Cell-mediated Immunity

A
  • production of activated T lymphocytes

- directly attack unwanted cells

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22
Q

Antigen

A
  • large, foreign, unique molecule
  • induces an immune response against itself
  • in general, more complex a molecule is the greater its antigenicity
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23
Q

B Lymphocytes

A
  • each lymphocyte has surface receptors for binding with one particular type of possible antigen
  • on binding with processed and presented antigen: most B cells differentiate into active plasma cells, other B cells become dormant- memory cells
24
Q

Plasma Cells

A
  • produce antibodies that can combine with a specific kind of antigen
  • all antibodies eventually enter blood: gamma globulins or immunoglobins
  • secreted into blood or lymph; depending on the location of the activated plasma cells
25
Q

B-CElls to Plasma Cells

A
  • produces antibodies

- greatly increased ER

26
Q

Antibody Subclasses (IgM)

A

serves as the B cell surface receptor for antigen attachment and is secreted in early stages of plasma cells response

27
Q

IgG

A
  • most abundant immunoglobulin in blood
  • produced in large amounts when body is exposed to same antigen
    • together IgM and IgG produce most specific response
28
Q

igE

A
  • helps protect against parasitic worms

- antibody mediator for common allergic responses

29
Q

IgA

A
  • found in secretions of digestive, respiratory, and genitourinary systems
  • also in milk and tears
30
Q

IgD

A
  • present on surface of many B cells

- function is uncertain

31
Q

B Lymphocytes Summary (plasma cells)

A
  • activated B-cell clones multiply and differentiate into: plasma cells
  • produce and secrete IgG antibodies
  • antibodies combines with an antigen, marking it for destruction
  • during initial contact with microbial antigen, antibody response is delayed and plasma cells are formed
  • peak is reached in a couple weeks by primary response
  • after peak, antibody concentration decreases
32
Q

Memory Cells Summary

A
  • small percentage of B lymphocytes become memory cells
  • remain dormant
  • upon re-exposure to same antigen; more ready for immediate action than the original lymphocytes of the clone
  • secondary response is quicker, more potent, and longer-lasting
  • can be induced by disease or vaccination
33
Q

Antibodies

A
  • y-shaped molecules
  • composed of four interlinked polypeptide chains; 2 long, heavy chains and 2 short, light chains
  • properties of tail portion determine functional properties of the antibody
  • identical antigen-binding fragments (Fab) at tip of each arm (unique for each different antibody)
  • tail (constant region) regions within each subclass are identical
34
Q

How Antibodies Eliminate Invading Microbes

A
  • neutralization
  • agglutination and precipitation; antibodies amplify innate immune responses by:
    1. activating the complement system
    2. enhancing phagocytosis by acting as opsonins
    3. stimulating killer cells
35
Q

Antibodies - Summary

A
  • can physically hinder antigens by:
    1. neutralization, they prevent harmful chemicals from interacting with susceptible cells
    2. bacterial toxins, viruses
  • can bind to foreign cells by agglutination; cells are clumped together
  • enhance activity of other defense systems by innate immune response1. activating
    1. complement system
    2. enhancing phagocytosis (opsonization)
    3. stimulating killer (K) cells
36
Q

Primary and Secondary Immune Responses

A
  • initial contact with antigen, antibody response is delayed for several days until plasma cells are formed
    VS
  • if same antigen reappears, long-lived memory cells launch more rapid, more potent, and longer-lasting response
  • more powerful attack is frequently adequate to prevent or minimize overt infection on subsequent exposures to the same microbe, forming the basis of long-term immunity against a specific disease
37
Q

Memory Cells

A
  • small percentage of B lymphocytes become memory cells
  • remain dormant
  • upon re-exposure to same antigen, they are more ready for immediate action than the original lymphocytes of the clone
  • secondary response is quicker, more potent, and longer lasting; can be induced by disease or vaccination
38
Q

Active Immunity

A
  • self-generated
  • results from exposure to an antigen
  • production of antibodies
39
Q

Passive Immunity

A
  • borrowed immunity
  • results from transfer of preformed antibodies
  • can provide immediate protection or bolster resistance; transfer of IgG antibodies from mother to fetus; Antibodies against rabies virus in nonimmunized person
40
Q

T Cells and Targets

A
  • carry out cell-mediated immunity
  • do not secrete antibodies; directly bind to targets
  • killer T cells release chemicals that destroy targeted cells
  • clonal and antigen specific; acquire receptors in the thymus
41
Q

T Lymphocytes

A
  • T cells are activated for foreign attack only when it is on the surface of a cell that carries foreign and self antigens (MHC)
  • learn to recognize foreign antigens only in combination with a person’s own tissue antigens
  • a few days are required before T cells are activated to launch a cell-mediated attack
  • express receptors for specific antigens (like B-lymphocytes)
42
Q

Cytotoxic and Helper T cells

A
  • clones mature in thymus:
  1. CD8 cells or cytotoxic T cells
    - destroy host cells harboring anything foreign
    - destruction of any self cells that are cancerous or infected with virus
    - require Class 1 MHC (all cells)
  2. CD4 cells (mostly Helper T cells)
    - modulates activities of other immune cells
  • secrete chemicals that amplify the activity of other immune cells:
  • B- cell growth factor
  • T-cell growth factor (interleukin-2)
  • macrophage-migration inhibition factor
  • regulatory T cells are a small subset
  • require Class 2 MHC (macrophages, B cells, dendritic cells)
43
Q

Memory T cells

A
  • form a memory pool
  • display both primary and secondary responses
  • primary responses tend to be initiated in the lymphoid tissues
  • within a few weeks, most dies off by apoptosis
  • remaining T cells become long-lived memory T cells
44
Q

T lymphocytes- Cell-Mediated Immunity

A

Antigen must be complexed with another cellular protein (unlike B-lymphocytes)

  • major histocompatibility complex (MHC)
  • identity tags for biological self
45
Q

Cytotoxic T Cells

A
  • target host cells infected with viruses
  • bind to the viral antigen and self-antigen on the surface of the infected cell
  • may kill cell directly or through enzymes which cause the cell to self-destruct
46
Q

Mechanism of Killing by Cytotoxic T Cells

A
  • perforin molecules
  • release granzymes to induce apoptosis (programmed cel death)
  • released virus dealt with by phagocytes, Ab and complement
47
Q

Helper T Cells

A
  • secrete cytokines
  • protein messages between immune cells
  • augment many aspects of immune responses:
    1. b cell growth factor
    2. interleukin-2
  • macrophage-migration inhibition factor
48
Q

Major Histocompatibility

A
  • plasma membrane-bound glycoproteins called MHC molecules
  • synthesis is directed by group of genes called major histocompatability complex (MHC)
  • exact pattern of MHC molecules varies from one individual to another
  • T cells have antigen receptors which recognize antigens
  • BUT only when they are associated with MHC molecules
  • antigen presentation
49
Q

2 Classes of MHC

A
  1. Class 1: MHC are expressed on the surface of all nucleated cells
  2. Class 2: MHC are expressed on immune system cells
    - macrophages, dendritic cells, activated B cells
50
Q

Antigen Presentation by Macrophage

A
  • lymphocytes respond only to antigens presented to them by antigen-presenting cells
  • macrophages can be antigen-presenting cells
  • phagocytosis occurs, processing the raw antigen intracellularly and presenting the processed antigen, exposing it to the outer surface of the macrophage’s plasma membrane
  • as macrophage engulfs and ingests microbe, it digests the microbe into antigenic peptides
  • antigenic peptides bind to a MHC molecule which transports the bound antigen to the cell surface where it is presented to passing lymphocytes
  • antigen-presenting macrophages secrete interleukin-1
51
Q

Cytokines

A
  • leukocytes secrete chemicals (cytokines) that help or augment nearly all aspects of the immune response
  • B cell and T cell growth factor
  • chemotaxins
  • macrophage-inhibition factor
52
Q

Immune System Tolerance

A
  • refers to preventing the immune system from attacking the person’s own tissues
  • mechanisms involved in tolerance:
  • clonal deletion
  • cells that recognize “self” are permanently destroyed during development
53
Q

Immune DIseases

A
  • due to abnormal functioning of the immune system
  • 2 general ways:
    1. immunodeficiency diseases: too little immune response
  • ex. severe combined immunodeficiency (lacking both B and T cells) and AIDS
    2. Inappropriate Immune Attacks: too much or mistargeted immune response
  • ex. autoimmune responses, immune complex diseases, allergies
54
Q

Autoimmune Diseases

A
  • the immune system treats a part of itself like an invading pathogen
  • ex. pancreas beta cells: type 1 diabetes mellitus
  • ex. tissues in joints: rheumatoid arthritis
55
Q

Allergy

A
  • acquisition of an inappropriate specific immune reactivity (hypersensitivity) to a normally harmless environmental substance
  • offending agent is known as an allergen
  • categories of allergic responses:
    1. immediate hypersensitivity
    2. delayed hypersensitivity
56
Q

Immediate HYpersensitivity

A
  • chemical mediators; histamine, eosinophil chemotactic factor
  • symptoms: vary depending on site, allergen, and mediators involved:
    hay fever, asthma, and hives
57
Q

Role of IgE Antibodies and Mast Cells in Immediate Hypersensitivity

A
  • B-cell clones are converted to plasma, which secrete IgE on contact with the allergen for which they are specific
  • tail binds to receptor proteins specific for IgE tails on mast cells and basophils
  • unlike B cells which mast cell bears a variety of antibody surface receptor specific for it on the surface of a mast cell, mast cell releases histamine and other chemicals
  • chemicals elicit allergic response

Human Physiology 2 (10 decks)

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