Body Defenses Flashcards
1
Q
Immunity/body’s defences involve the body’s ability to eliminate…
A
- potentially harmful foreign substances (microbes)
- abnormal and cancerous cells or mutant cells originated in the body
- the substances are “foreign” or “non-self” to the body
- reject the tissue cells of foreign origin
- worn out RBCs, tissue debris and invading pathogens
- mounting inappropriate immune responses to allergies
2
Q
If the body’s defences fail to work…
A
inappropriate immune responses can occur, allergies to environmental chemicals, autoimmune diseases
3
Q
Innate immune system
A
- non-specific/first line of defence
- responses are rapid but limited and work immediately when the body is exposed to threatening agents
- non-selectively defend against foreign invaders
- uses toll-like receptors (TLRs) as the “eyes” of the innate immune system
- do not involve antibody production
4
Q
Cells of the innate immune system
A
neutrophils, macrophages, basophils, natural killer cells
5
Q
Adaptive or acquired/specific immune system
A
- specifically targets foreign material to which the body has already been exposed
- the body takes time to prepare to attack
- it is an ultimate weapon against most pathogens
- responses are mediated by B and T lymphocytes
- the formation of memory cells allows the system to react more swiftly against specific invaders in the future
- involves specific secretion (antibodies)
6
Q
Cells of the adaptive immune system
A
T cells, B cells and plasma cells
7
Q
Non-specific responses are ___ or ___-__- defence mechanisms
A
Non-specific responses are inherent or built-in- defence mechanisms
8
Q
Innate immune defenses provide a first line of defense against …
A
infectious agents, chemical irritants or tissue injury from mechanical trauma and burns
9
Q
Physical/External defenses prevents …
A
microbial invasion upon the body’s exposure to the external environment
10
Q
The physical/external defences consist of the following…
A
the skin/integument, the digestive system, the genitourinary system and the respiratory system
11
Q
Physical/external defense: The skin
A
- mechanical barrier
- keratinized layer (skin)
- epidermal enzymes
- sweat and chemicals (sebaceous gland)
- Langerhans cells (the skin)- antigen-presenting cells (APC)
- skin-associated lymphoid tissue (SALT)
12
Q
Physical/external defense: digestive system
A
- salivary enzymes lyse ingested bacteria
- bacteria in the oral cavity convert nitrate into nitrite and nitrite to nitrogen oxide in the stomach (acidification)
13
Q
Physical/external defense: The genitourinary system
A
- acidic urine and acidic vaginal secretions lyse certain bacteria
- mucus- entraps small invading particles
14
Q
Physical/external defense: The respiratory system
A
- nasal hair
- lymphoid tissue (tonsils and adenoids)
- alveolar macrophages
- coughs and sneeze
15
Q
Innate immune defences are divided into …
A
physical/external and chemical/internal
16
Q
Chemical/internal defenses
A
first line of defense, non-specific, rapid but limited response
17
Q
Chemical/internal defenses include the following…
A
- interferon
- complement system
- inflammation
- natural killer cells (NK)
18
Q
Interferon and viruses
A
1) Virally infected cell
2) Release interferon (IFN)
3a) act as “whistle blower” to..
3a’) triggers the production of viral blocking enzymes in healthy cells to ..
4a) warn healthy neighbouring cells of
potential viral attack
4a’) breakdown the viral mRNA and inhibit protein synthesis in host/healthy cells
19
Q
Interferon also performs the following functions..
A
- enhances macrophage phagocytic activity and antibody production
- exerts anticancer (NK cells) and antiviral effects (T-cells)
- slows cell division and suppresses tumor growth
- enhances the actions of NK cells, T lymphocytes, cytotoxic T-cells to attack and destroy both virally-infected and cancerous cells
20
Q
The complement system
A
- exposure to CHO chains on the surface of microorganisms or the exposure to antibodies against a specific invader
- activates the complement system
- directly lyse the invaders
21
Q
The complement system “compliments” the action of ..
A
antibodies to kill foreign cells by forming membrane attack complexes (MAC)
22
Q
Formation of MAC
A
- Liver complements C1
- activates C2, C5 and C9
- components C5-C9 assemble to form membrane attack complex (MAC)
- this punches holes in the surface membrane of the victim’s cell
- makes membrane extremely leaky and causes entry of water by osmosis
- victim cell swell and burst
23
Q
Summary of the innate immune defenses:
Interferon=
The complement system=
Inflammation=
Natural killer cells=
A
Interferon= non-specifically defend against viral infection
Complement system= destroy the foreign cells by forming MAC
Inflammation= a non-specific response to tissue injury with the help of macrophages and neutrophils
Natural killer cells= non-specifically lyse and destroy virally-infected host cells and cancerous cells
24
Q
Inflammation
A
- non-specific immune response to foreign material or tissue damage
- an essential innate response to microbial invasion
- consists of highly interrelated events set in motion in response to foreign material, tissue damage or both
- attracts phagocytes and plasma proteins to an invaded or injured area that isolate, destroy, or inactivate the invaders, remove debris and prepare for subsequent healing and repair
25
Nitric Oxide (NO): secreted by and function
Secreted by: macrophages
Function: toxic to nearby microorganisms
26
Lactoferrin: secreted by and function
Secreted by: neutrophils
Function: protein that binds with iron, making it unavailable for use by invading bacteria
27
Histamine: secreted by and function
Secreted by: mast cells
Function: induces local vasodilation and increases capillary permeability
28
Kallikrein: secreted by and function
Secreted by: neutrophils
Function: converts specific plasma proteins precursors produced by liver into activated kinins
29
Endogenous pyrogen (EP): secreted by and function
Secreted by: macrophages
Function: induces development of fever
30
Leukocyte endogenous mediator (LEM): secreted by and function
Secreted by: macrophages
Function: decreases the plasma concentration of iron by altering iron metabolism within the liver, spleen and other tissues, also stimulates synthesis and release of neutrophils by the bone marrow
31
Acute phase proteins: secreted by and function
Secreted by: Liver upon stimulation by LEM
Function: play role in inflammatory process, tissue repair, and immune cell activities
32
C-reactive protein: secreted by and function
Secreted by: Liver
Function: specific acute phase protein that is clinically used as a blood-borne marker of inflammation
33
Interleukin 1 (IL-1): secreted by and function
Secreted by: macrophages
Function: enhances proliferation and differentiation of B and T lymphocytes
34
Sequences of the inflammation
- defense by resident tissue macrophages
- localized vasodilation
- increased capillary permeability
- localized oedema
- walling off the inflamed area
- emigration of leukocytes
- leukocyte destruction of bacteria
- mediation of the inflammatory response by phagocyte-secreting chemicals
- tissue healing and repair
35
Defense by resident tissue macrophages
- they are stationary but become mobile and migrate to the invaded tissue
- begin to phagocytose foreign microbes when entering through the skin
36
Localized vasodilation
- bacterial invasion at injured tissue
- attracts mast cells
- release histamine
- enhances arteriolar dilation, increasing the blood flow and velocity to the injured tissue
- this brings more phagocytic leukocytes and plasma proteins
37
Increased capillary permeability
- mast cells at injured site
- release histamine
- increases capillary's permeability by enlarging the capillary pores
- this allow the leakage of proteins from the blood to enter the inflamed area
38
Localized edema
- accumulation of plasma proteins in the interstitial fluid
- elevate the local interstitial fluid colloid osmotic pressure
- tend to move fluid out of capillary and accumulate in the injured area
- this causes edema (swelling)
- also causes symptoms of inflammation
- pain is caused by the distension of swollen tissue and substances released by injured tissues (prostaglandins)
39
Cardinal signs of inflammation
heat, redness, swelling, pain and loss of function
40
Walling off the inflamed area
- leaked plasma proteins also bring thromboplastin- thrombin
- converts fibrinogen into fibrin
- forms a clot around the bacterial invader and damaged tissue
- this walling off inflamed area prevent the spread of invaders and their toxic products to a nearby tissue
41
Leukocytes are emigrated to the injured and invaded tissue by
margination, diapedesis, chemotaxis
42
Emigration of leukocytes
- inflamed tissue attracts neutrophils (within 1 hr) and monocytes (8-12 hrs of injury) from blood
- these leukocytes attach to the inner endothelial lining of the capillaries in the affected area (margination)
- CAM (cell adhesion molecule-selectin) protrude from endothelial lining slows down the leukocytes and rolls them along the vessel lining
- gives enough time for leukocytes to check for local activating factors (SOS signals) from nearby injured tissues
- these factors cause leukocytes to adhere firmly to the endothelial lining
- adhered leukocytes leave the capillaries by diapedesis and move toward the injured sites (neutrophils come first)
- inflamed tissue release chemical mediators- chemokines which will attract phagocytic cells by a process called chemotaxis
- phagocytic cell increases Ca2+ entry into the cell
- Ca2+ then switches cellular contractile apparatus to lead the crawling of phagocytic cells toward the inflamed tissue
43
Damaged tissue --> ___ --> __
Damaged tissue --> chemokines --> Ca2+
44
Leukocyte proliferation
- inflamed tissue releases "chemical mediator"
- this causes the bone marrow to proliferate a larger number of neutrophils, monocytes and macrophages to eliminate invaders and heal the tissue
45
Marking of bacteria for destruction by opsonin
- opsonins- C3b (produced by the liver) attach to the TLRs on the phagocytes
- opsonin increases phagocytosis by linking the foreign cell to a phagocytic cell
46
Mechanism of opsonin action
one of the activated complement molecules, C3b, links a foreign cell, such as a bacterium, and a phagocytic cell by nonspecifically binding with the foreign cell and specifically binding with a receptor on the phagocyte. This link ensures that the foreign victim does not escape before it can be engulfed by the phagocyte
47
Leukocyte destruction of bacteria
- macrophages and neutrophils release hydrolytic enzymes (lysosomes)
- these will break down and phagocytose the bacteria and trapped material
- this forms a pus (collection of dead and live neutrophils, macrophages, lysosomal enzymes from phagocytes and bacteria)
48
Microbe-stimulated phagocytes release many chemical mediators. These mediators/chemicals include..
- chemicals that are highly destructive to microbes
- neutrophils secrete lactoferrin and NO
- a lack of iron in lactoferrin decreases the multiplication of the bacteria
- phagocytic secretion stimulates histamine from mast cells which induce local vasodilation and vascular permeability
- some phagocytic chemical mediators trigger both clotting and anti-coagulating systems to enhance the walling off process and then the dissolution of the clot
49
Tissue repair
fibroblast rapidly divide in the vicinity and secrete large amount of collagen to fill the vacated region of the injured tissue to form scar tissue
50
Natural Killer (NK) cells
- 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
51
2 classes of adaptive immunity
1. antibody-mediated or humoral immunity
2. cell-mediated immunity
52
Antibody-mediated/humoral immunity
- involves the production of antibodies by beta lymphocyte derivatives known as plasma cells
- b cells recognize and respond to bacteria and their toxins and a few viruses
53
Cell-mediated immunity
- involves the production of activated T lymphocytes- directly attack unwanted cells, such as virally infected and cancerous cells
54
Antigen
- a surface protein molecule present on microbes and tag a microbe as a "foreigner"
- antigen stimulates b cells to proliferate and differentiate into plasma cells to produce antibodies
55
Antibody
- a protein molecule synthesized by plasma cell in response to a specific antigen/foreign material
- antibodies neutralize and agglutinate antigen-antibody complexes
56
Antibody structure
- y shaped molecule
- composed of 4 interlinked polypeptide chains (2 long heavy chains and 2 short light chains)
- antigen-binding site (Fab) of Y region- specificity
- properties of tail portion (Fc) region- functional properties of the antibody
- tail (constant region, Fc) regions within each subclass are identical
57
IgM
- serve as the b-cell surface receptor for antigen attachment
- secreted in the early stages of plasma cell response
58
IgG
- most abundant in the blood
- produced when the body is exposed to the same antigen
- also enhances phagocytosis
59
IgE
- helps protect against parasitic worms
- is the immune mediator for common allergic responses
60
IgA
found in the secretion of the digestive, respiratory and genitourinary systems, milk (breast milk) and tears
61
IgD
is present on the surface of many B cells, function is uncertain
62
antibodies responsible for most specific immune responses against bacterial invaders and few types of viruses
IgG and IgM
63
Antibody-mediated immunity against bacteria
macrophage-antigen presenting cells (APC) present part of the antigen to B-cells which proliferate and differentiate into plasma cells to produce specific antibodies that neutralize sp. antigen
64
activated b-cell clones multiply and differentiate into either ...
plasma or memory cells
65
plasma cells
- produce and secrete IgG antibodies
- antibody combines with an antigen, marking it for destruction
- during initial contact with microbial antigen, the antibody response is delayed, and plasma cells are formed
-the peak is reached in a couple of weeks by the primary response
- after the peak, antibody concentration decreases
66
memory cells
- a small percentage of b lymphocytes become memory cells
- remain dormant
- upon re-exposure to the same antigen, they are more ready for immediate action than the original lymphocytes of the clone
- the secondary response is quicker, more potent and longer-lasting
67
Neutralization
- antibodies can prevent/hinder some antigens from exerting their detrimental effects
- they can bind to some viruses and prevent them from entering into neighbouring cells
- binding antibodies with bacterial toxins prevents toxins from interacting with cells
68
Antigen-antibody complexes
binding of many antibodies to many antigens forms a chain or lattices
69
Precipitation
when antigen-antibody complexes involve soluble antigen (toxins), lattices or chain becomes large and separate out from solution (become prominent on plasma)
70
Agglutination
a process by which foreign cells (bacteria) or mismatched transfused RBC, bind together as "clump"- nearby macrophages engulf them
71
Active immunity
- "self-generated"
- results from exposure to an antigen
72
Passive immunity
- "borrowed immunity"
- results from the transfer of preformed antibodies
- it can provide immediate protection or bolster resistance
- an example is a transfer of IgG antibodies from the mother to the fetus
73
Cell-mediated immunity T-lymphocytes
- carry out cell-mediated immunity (accounts for 50-70% of the total body's lymphocytes)
- do not secrete antibodies- directly bind to targets
- killer T cells release chemicals that destroy targeted cells
- t cells are activated for foreign attack only when it is on the surface of a cell that carries foreign and self-antigens (MHC I and II)
- 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
74
two main types of T cells
CD8 and CD4 cells
75
CD8 cells (cytotoxic/killer T cells)
destroy host cells harbouring anything foreign
76
CD4 cells (mostly helper T cells)
- modulate 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) and macrophage-migration inhibition factor)
77
Self-antigens
- plasma membrane-bound glycoproteins called MHC molecules
- synthesis is directed by a group of genes called major histocompatibility complex (MHC)
-the exact pattern of MHC molecules varies from one individual to another
78
MHC I
- found on the surface of all cells
- are recognized only by cytotoxic T cells
- CD8 coreceptor links the two cells together
- linked in this way, cytotoxic T cells can destroy body cells if invaded by foreign (viral) antigen
79
MHC II
- found on the surface of immune cells with which helper T cells interact (dendritic cells, macrophages and B cells)
- they are recognized only by helper T cells
- CD4 coreceptor links the two cells together
- to be activated, helper T cells must bind with a class II MHC-bearing APC (dendritic cell or macrophage). To activate B cells, helper T cell must bind with a class II MHC-bearing B cell with displayed foreign antigen
80
Which statement is correct for leukocytes?
a. they are responsible for the body's various immune defence strategies
b. they spend most of their time circulating in the blood
c. they are all produced in the lymph nodes
d. they are responsible for the body's various immune defence strategies and spend most of their time circulating in the blood
A
81
Which of the following is NOT attributable to the immune defence system?
a. it defends against pathogenic microorganisms
b. it converts foreign chemicals into compounds that can be more readily eliminated in the urine
c. it removes worn-out cells and tissue debris
d. it identifies and destroys abnormal or mutant cells
B
82
Which of the following is NOT part of the inflammatory response?
a. localized vasodilation
b. migration of neutrophils and macrophages to the site of injury
c. kinin activation
d. interferon inhibition of viral replication
D
83
Which of the following is correct for interferon?
a. it is a family of proteins that defends against viruses
b. it is a natural killer cell
c. it is a specific bacterial surface receptor
d. it is a specialized type of white blood cell
A
84
Which statement is correct for opsonins?
a. they enhance phagocytosis by linking foreign cell to a phagocytic cell
b. they are secreted by phagocytes
c. they include antibodies and one of the activated proteins of the complement system
d. they both enhance phagocytosis by linking the foreign cell to a phagocytic cell and include antibodies and one of the activated proteins of the complement system
D
85
Which statement is correct for diapedesis?
a. diapedesis refers to the process of white blood cells engulfing and destroying invading organisms
b. diapedesis refers to the process of leukocytes squeezing through pores of the capillary wall into the surrounding interstitial fluid
c. diapedesis refers to the attraction of white blood cells to areas of injury, inflammation, and bacterial invasion
d. diapedesis is a feature exhibited by platelets
B
86
What is the primary purpose of the vascular changes in an invaded or injured area?
a. they produce swelling, redness, heat and pain
b. they bring to the affected area phagocytes and plasma proteins that defend against the offending agent
c. they produce pus
d. they exert an anti-inflammatory effect to protect against damage by potentially overreactive defence mechanisms
B
87
Which statement is correct for T lymphocytes?
a. they produce thymosin
b. they secrete antibodies
c. they are converted into plasma cells
d. they mature and differentiate within the thymus gland
D
88
Which statement is correct for B lymphocytes?
a. they are responsible for antibody-mediated immunity
b. they are activated by thymosin
c. they mature and differentiate into macrophages
d. they bind with foreign antigen in association with self-antigen
A
89
Which of the following is correct for plasma cells?
a. they are derived from T cells
b. they have an expanded rough endoplasmic reticulum
c. they do not secrete antibodies but remain dormant and expand the clone specific for the invading antigen
d. they are derived from T cells and have an expanded rough endoplasmic reticulum
B
90
Which of the following is NOT accomplished by antibodies?
a. neutralization of bacterial toxins
b. direct destruction of foreign body cells
c. activation of the complement system
d. enhancement of phagocytosis
B
91
Which of the following regarding IgM immunoglobulin is correct?
a. it serves as the B-cell surface receptor for antigen attachment
b. it is found in milk and tears
c. it mediates common allergies such as hay fever, asthma, and hives
d. it is the most abundant antibody produced by plasma cells
A
92
Which of the following does NOT apply to macrophages?
a. they participate in inflammation
b. they process and present antigen to lymphocytes
c. they secrete antibodies
d. they participate in immune surveillance against cancer
C
93
Which type of immune defence cell is selectively invaded by the AIDS virus?
a. cytotoxic T cells
b. helper T cells
c. suppressor T cells
d. macrophages
B
94
Lymphocytes respond only to antigens that have been processed and presented to them by which of the following?
a. neutrophils
b. eosinophils
c. macrophages
d. helper T cells
C
95
Which of the following is NOT found in the epidermis?
a. blood vessels whose calibre can be adjusted as part of the temperature regulatory mechanisms
b. keratinocytes
c. melanocytes
d. Langerhans cells
A
96
Which of the following does NOT contribute to defence of the respiratory system?
a. coughs and sneezes
b. cilia-propelled mucus escalator
c. alveolar macrophages
d. normal microbial population of the lungs
D
97
True/False:
Pathogenic bacteria induce tissue damage and produce disease by invading host cells and taking over the cellular biochemical facilities for their own purposes
False
98
True/False:
Immune surveillance refers to the body's ability to resist or eliminate potentially harmful foreign invaders
False
99
True/False:
Diapedesis is the means by which a leukocyte reproduces
False
100
True/False:
Endogenous pyrogens released by macrophages cause the hypothalamus to elevate body temperature during times of infection
True
101
True/False:
During their agglutination, red blood cells clump together
True
102
True/False:
The arm regions of an antibody determine with what antigen the antibody can bind, whereas the tail portion determines the destiny of the antibody once it is bound
True
103
True/False:
Cytotoxic T cells are one of several kinda of regulatory T cells
True
104
True/False:
Saliva is destructive to bacteria because it is highly acidic
False
105
____ refers to the body's ability to resist or eliminate potentially harmful foreign materials or abnormal cells
Immunity
106
Adhesion of blood-borne leukocytes to the endothelial lining is known as ____
margination
107
____ refers to the chemical attraction of leukocytes to the site of invasion
Chemotaxis
108
A pyrogen induces the development of ____
fever
109
The inflammatory agent ___ is released by mast cells
histamine
110
The T lymphocyte lineage undergoes maturational processing and differentiation in the ___
thymus
111
Most of the progeny of an activated B-cell clone differentiate into ___ ____, which produce antibodies, and ___ ___ which remain dormant and expand the specific clone
Most of the progeny of an activated B-cell clone differentiate into plasma cells, which produce antibodies, and memory cells which remain dormant and expand the specific clone
112
Antibody proteins consist of two heavy and ___ light polypeptide chains
two
113
Does this apply to the Fab region or Fc region:
Located in the "arm" regions of an antibody
Applies to the Fab region
114
Does this apply to the Fab region or Fc region:
Located in the "tail" regions of an antibody
Applies to the Fc region
115
Does this apply to the Fab region or Fc region:
Highly variable between different antibodies of the same class
Applies to the Fab region
116
Does this apply to the Fab region or Fc region:
Constant between different antibodies
Applies to the Fc region
