Ch. Ten: Body Defences Flashcards
(57 cards)
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
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
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
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
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
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
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
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
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
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
11
Q
Leukocyte Emigration From the Blood
A
- chemotaxis: chemicals released initiate rolling (margination) and migration
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
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
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
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
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
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
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
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
20
Q
Antibody-mediated (humoral immunity)
A
- production of antibodies by activated B lymphocytes= plasma cells
21
Q
Cell-mediated Immunity
A
- production of activated T lymphocytes
- directly attack unwanted cells
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
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
B-CElls to Plasma Cells
- produces antibodies
| - greatly increased ER
26
Antibody Subclasses (IgM)
serves as the B cell surface receptor for antigen attachment and is secreted in early stages of plasma cells response
27
IgG
- 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
igE
- helps protect against parasitic worms
| - antibody mediator for common allergic responses
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IgA
- found in secretions of digestive, respiratory, and genitourinary systems
- also in milk and tears
30
IgD
- present on surface of many B cells
| - function is uncertain
31
B Lymphocytes Summary (plasma cells)
- 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
Memory Cells Summary
- 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
Antibodies
- 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
How Antibodies Eliminate Invading Microbes
- 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
Antibodies - Summary
- 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
Primary and Secondary Immune Responses
- 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
Memory Cells
- 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
Active Immunity
- self-generated
- results from exposure to an antigen
- production of antibodies
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Passive Immunity
- 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
T Cells and Targets
- 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
T Lymphocytes
- 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
Cytotoxic and Helper T cells
- 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
Memory T cells
- 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
T lymphocytes- Cell-Mediated Immunity
Antigen must be complexed with another cellular protein (unlike B-lymphocytes)
- major histocompatibility complex (MHC)
- identity tags for biological self
45
Cytotoxic T Cells
- 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
Mechanism of Killing by Cytotoxic T Cells
- perforin molecules
- release granzymes to induce apoptosis (programmed cel death)
- released virus dealt with by phagocytes, Ab and complement
47
Helper T Cells
- 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
Major Histocompatibility
- 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
2 Classes of MHC
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
Antigen Presentation by Macrophage
- 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
Cytokines
- 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
Immune System Tolerance
- 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
Immune DIseases
- 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
Autoimmune Diseases
- 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
Allergy
- 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
Immediate HYpersensitivity
- chemical mediators; histamine, eosinophil chemotactic factor
- symptoms: vary depending on site, allergen, and mediators involved:
hay fever, asthma, and hives
57
Role of IgE Antibodies and Mast Cells in Immediate Hypersensitivity
- 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
