Chapter 21: Lymphatic and Immune Flashcards
1
Q
List the functions of the lymphatic system
A
Fluid recovery, immunity, and lipid absorption
2
Q
Describe how the lymphatic system aids in fluid recovery
A
-Fluid continually filters from the blood capillaries into the tissue spaces
-15% (~3 L/day) of enter the lymphatic system
-Any lost plasma proteins, chemicals, pathogens washed into lymphatic system
3
Q
Describe how the lymphatic system aids in immunity
A
Fluid passes through lymph nodes where immune cells activates a protective immune response
4
Q
Describe how the lymphatic system aids in lipid absorption
A
Lacteals in the small intestine absorb dietary lipids that are not absorbed by the blood capillaries
5
Q
What are the 4 main components of the lymphatic system?
A
Lymph, lymphatic vessels, lymphatic tissues, and lymphatic organs
6
Q
What are aggregates of lymphocytes and macrophages that populate many organs called?
A
Lymphatic tissues
7
Q
What contains a concentration of defense cells and is separated from surrounding organs by connective tissue capsules?
A
Lymphatic organs
8
Q
Describe lymph
A
-A clear, colorless fluid, similar to plasma, but much less protein
-Originates as interstitial fluid drawn into lymphatic capillaries
-Chemical composition varies in different places (in intestines, after lymph nodes)
9
Q
How does lymph differ from plasma?
A
It has much less protein
10
Q
What does lymph originate as?
A
Originates as interstitial fluid drawn into lymphatic capillaries
11
Q
True or false: the chemical composition of lymph varies in different places (in intestines, after lymph nodes)
A
True
12
Q
Lymphatic vessels are a one-way system that flows towards what?
A
The heart
13
Q
What is the order of movement of lymph through the lymphatic vessels?
A
1) Lymphatic capillaries
2) Lymphatic collecting vessels
3) Lymphatic trunks
4) Lymphatic ducts
14
Q
Lymphatic capillaries penetrate nearly every tissue of the body, but where are they absent?
A
The bone marrow, central nervous system, and tissues, (such as the epidermis)
15
Q
Describe the lymphatic capillaries (terminal lymphatics)
A
-They penetrate nearly every tissue of the body
-Very permeable
-Overlapping endothelial cells form one-way valves so fluid can enter but can’t exit
16
Q
What forms the one-way valves of the lymphatic capillaries?
A
Overlapping endothelial cells
17
Q
What 3 layers are larger lymphatic vessels composed of? Describe them.
A
1) Tunica interna: endothelium and one-way valves
2) Tunica media: elastic fibers, smooth muscle
3) Tunica externa: thin outer layer
18
Q
Describe the lymphatic vessels
A
-Converge into larger and larger vessels
-Collecting vessels course through many lymph nodes
-Larger ones are composed of tunica interna, tunica media, and tunica externa
19
Q
What course through many lymph nodes?
A
Collecting vessels
20
Q
What are lymphatic vessels most similar to?
A
Veins
21
Q
How many lymphatic trunks drain major portions of body?
A
11
22
Q
What are the two collecting ducts?
A
Right lymphatic duct and thoracic duct
23
Q
Compare the speed and pressure of lymph flow to that of blood
A
Low pressure & slower speed than venous blood
24
Q
What 4 things allow lymph to flow?
A
-Rhythmic contractions of lymphatic vessels (stretching wall stimulates contraction)
-Skeletal muscle pump
-Arterial pulsation
-Thoracic pump
25
What can you do to significantly increase your lymphatic return?
Exercise
26
Name the 6 lymphatic cells
1) Natural killer (NK) cells
2) T-lymphocytes (T-cells)
3) B-lymphocytes (B-cells)
4) Macrophages
5) Dendritic cells
6) Reticular cells
27
Describe natural killer (NK) cells and what they kill
Large lymphocytes that attack bacteria, transplanted tissue, viral-infected cells or cancer
28
What type of lymphatic cell matures in the thymus?
T lymphocytes (T cells)
29
Describe macrophages
-Large phagocytes that develop from monocytes
-Works as Antigen-presenting cells (APCs) for T cells
30
Describe dendritic cells
Branched, mobile antigen-presenting cells found in epidermis, mucous membranes, and lymphatic organs
31
What do reticular cells do?
They form the stroma (soft skeleton) of a lymphatic organ
32
Define lymphatic tissues
Aggregations of lymphocytes in the connective tissues of mucous membranes and various organs
33
Describe diffuse lymphatic tissue and in which 4 systems it's found
-Lymphocytes scattered
-Mucosa-associated lymphatic tissue (MALT)
-Which 4 systems? Reproductive, urinary, digestive, and respiratory
34
Describe lymphatic nodules (follicles) and where they're found
Dense masses found in lymph nodes, tonsils, appendix, and Peyer patches
35
Name the two primary lymph organs and what they do
-Red bone marrow and thymus
-The thymus is where T cells become activated: able to recognize and respond to antigens
36
Name 3 secondary lymph organs and briefly describe them
-Includes the lymph nodes, tonsils, and spleen
-Immunocompetent cells populate these tissues
37
What two things is red bone marrow involved in?
Hemopoiesis (blood formation) and immunity
38
Describe the red bone marrow and its role in immunity
-Soft, loosely organized, highly vascular material
-Separated from osseous tissue by endosteum of bone
-As blood cells mature, they push their way through the reticular and endothelial cells to enter the sinus and flow away in the bloodstream
39
Describe the thymus
-A bilobed organ located in superior mediastinum
-Shows degeneration (involution) with age
-The lobules are divided into cortex and medulla
40
Describe what the thymus does
-T Lymphocytes develop in the thymus's cortex, then move to its medulla
-Produces signaling molecules thymosin, thymopoietin, thymulin, interleukins, and interferon
41
What organ produces signaling molecules thymosin, thymopoietin, thymulin, interleukins, and interferon. What line of defense is this?
Thymus; second line of defense
42
What is the most numerous lymphatic organ?
Lymph nodes
43
What are the 2 functions of lymph nodes?
-Cleanse the lymph
-Act as a site of T and B cell activation
44
Describe the general anatomy of lymph nodes
45
Describe the general anatomy of lymph nodes
-An elongated, bean-shaped structure with hilum
-It's enclosed with a fibrous capsule with trabeculae that divide interior into compartments
46
What are the 2 major regions of the lymph nodes?
Cortex and medulla
47
What allows time for lymph to be cleaned?
-Several afferent lymphatic vessels lead into a lymph node along its convex surface, but there are only 1-3 efferent lymphatic vessels leave the hilum.
-This difference in the number of "entrances" and "exits" allows time for lymph to be cleaned
48
How are lymph nodes named?
For their location
49
Define lymphadenitis
A swollen, painful lymph node responding to foreign antigen
50
Define metasis
Cancerous cells break free from original tumor, travel to other sites in the body, and establish new tumors
51
Describe how metastatic cancer affects the lymphatic system
-Metastasizing cells easily enter lymphatic vessels, and they tend to lodge in the first lymph node they encounter. Usually makes them swollen and firm, but painless.
-They multiply there and eventually destroy the node
-They tend to spread to the next node downstream
52
What is the treatment for breast cancer? Why?
Treatment of breast cancer is lumpectomy, mastectomy, along with removal of nearby axillary nodes (since metastasizing cells easily enter lymph nodes)
53
Define and describe tonsils
-Defined as patches of lymphatic tissue located at the entrance to the pharynx that guard against ingested or inhaled pathogens
-They're covered with epithelium and have deep pits called tonsillar crypts, which are lined with lymphatic nodules
-Sometimes removed due to chronic tonsillitis via tonsillectomy
54
What is the body's largest lymphatic organ?
The spleen
55
List and describe the two types of tissue found in the spleen
1) Red pulp: sinuses filled with erythrocytes
2) White pulp: lymphocytes, macrophages surrounding small branches of splenic artery
56
What 3 things does the spleen do?
1) Responsible for blood cell production in fetuses (and very anemic adults); old RBC's are also often broken and disposed of here.
2) Stabilizes blood volume through plasma transfers to lymphatic system
3) White pulp monitors blood for foreign antigens and keeps an army of monocytes for release when needed
57
What does the white pulp of the spleen do?
Monitors blood for foreign antigens and keeps an army of monocytes for release when needed
58
Define pathogens
Agents capable of producing disease
(Includes viruses, bacteria, and fungi)
59
What are the 3 lines of defense against pathogens?
1) First line of defense: skin and mucous membranes
2) Second line of defense: several innate defense mechanisms
3) Third line of defense: adaptive immunity; defeats a pathogen, and leaves the body with a “memory” of it so it can defeat it faster in the future
60
Define innate defenses and list its 3 types
-Defenses that guard equally against a broad range of pathogens; local, nonspecific, and lacks memory
-Three kinds of innate defenses:
1) Protective proteins
2) Protective cells
3) Protective processes
61
Define adaptive immunity
-When the body develops immunity that's specific to a particular pathogen
-Body adapts to a pathogen and wards it off more easily upon future exposure (memory)
62
Name 4 external barries
1) Skin
2) Mucous membranes
3) Acid mantle
4) Fluid flow
63
Describe how the skin functions as an external barrier
-Toughness of keratin
-Too dry and nutrient-poor for microbial growth
-Dermicidin, defensins, and cathelicidins that kill microbes
64
Describe how mucous membranes function as an external barrier. In what body systems can they be found?
-Mucus physically traps microbes
-Lysozyme: enzyme destroys bacterial cell walls
-Found in respiratory, digestive, reproductive, and one more body system (**)
65
Describe how the acid mantle functions as an external barrier. Where is it most present?
-Lower pH inhibits bacterial and fungal growth
-Ex: Sweat, Sebum, Vagina, Stomach
66
Describe how fluid flow acts as an external barrier, and give 4 examples
-The penetration of microbes slowed by moving them out of susceptible area
-Ex: Urination, salivation, lacrimation, and mucus-ciliary escalator
67
What 3 things does the second line of defense consist of?
1) Protective cells
2) Protective proteins
3) Protective responses
68
Give 3 examples of protective cells
Leukocytes, Macrophages, and Natural Killer (NK) cells
69
Give 2 examples of protective proteins
Interferons and Complement proteins
70
Give 2 examples of protective responses
Fever and Inflammation
71
Define phagocytes
cells that engulf foreign matter
72
Describe how neutrophils act as a second line of defense
-Can kill bacteria using phagocytosis and digestion, or a respiratory burst
-Lysosomes degranulate releasing bactericidal chemicals; creates a killing zone around neutrophil
73
Describe how eosinophils act as a second line of defense
-They guard against parasites, allergens (allergy-causing agents), and other pathogens
-They kill tapeworms and roundworms by producing superoxide, hydrogen peroxide, and toxic proteins
74
In what two ways do basophils act as a second line of defense?
-Secrete Histamine: promotes inflammation
-Heparin: inhibits clot formation
75
Describe how mast cells act as a second line of defense
-Secrete histamine and heparin like basophils
-Type of connective tissue cell very similar to basophils
76
Define monocytes
Leukocytes that leave blood and transform into macrophages
77
List and describe the 2 primary types of macrophages
1) Wandering macrophages: actively seek pathogens
2) Fixed macrophages: phagocytize only pathogens that come to them
78
Give 3 examples of fixed macrophages
Microglia—in central nervous system
Alveolar macrophages (Dust cells) —in lungs
Hepatic macrophages—in liver
79
List the 3 types of lymphocytes found in circulating blood and their abundances
80% T cells
15% B cells
5% NK (Natural Killer) cells
80
Briefly describe the functions of lymphocytes
They have many diverse functions
NK cells are part of innate immunity, all others are part of adaptive immunity; helper T cells function in both
81
Define natural killer cells and what they do
They're a type of lymphocyte that continually patrols the body looking for pathogens and diseased host cells
82
What do natural killer (NK) cells kill?
NK cells attack and destroy bacteria, transplanted cells, cells infected with viruses, and cancer cells
83
How do natural killer (NK) cells kill things? (3 steps)
1) They recognize an enemy cell and bind to it
2) Release proteins called perforins that create pores in the cell
3) Secrete granzymes that induce apoptosis (programmed cell death)
84
Define antimicrobial proteins and list the 2 types
-Defined as proteins that inhibit microbial reproduction and provide short-term, Innate Immunity to pathogenic bacteria and viruses
-The two families of antimicrobial proteins are:
1) Interferons
2) Complement system
85
Describe interferons
-A type of antimicrobial protein secreted by certain cells infected by viruses that alert neighboring cells and protects them from becoming infected.
-Of no benefit to the cell that secretes them.
-Bind to surface receptors on neighboring cells and activates second-messenger systems within, and the alerted cell synthesizes anti-viral proteins
-Also activates NK cells and macrophages
86
Define a complement system
A group of 30 or more globular proteins
87
What are complement systems important for, where are they synthesized, and in what form do they circulate in blood?
-Important in both innate immunity & adaptive immunity
-Synthesized mainly by liver
-Circulate in the blood in inactive form
88
What are complement systems activated by?
The presence of a pathogen
89
What are the 4 methods in which a complement system aids in immune defense after being activated by a pathogen?
Inflammation
Immune clearance
Phagocytosis
Cytolysis
90
Describe how complement systems activate inflammation
-Stimulates mast cells and basophils to secrete histamine
-Activates and attracts neutrophils and macrophages
91
Describe how immune clearance is activated by the complement systems
-Binds with antigen–antibody (Ag-Ab) complexes to red blood cells
-When these RBCs circulate through liver and spleen, macrophages strip off and destroy the Ag–Ab complexes leaving RBCs unharmed
-It's the principal means of clearing foreign antigens from the bloodstream
92
What is the principal means of clearing foreign antigens from the bloodstream?
Immune clearance
93
Describe how phagocytosis is activated by the complement systems
Assists phagocytes by opsonization (coating microbial cells)
94
Describe how cytolysis is activated by the complement system
-Forms a Membrane Attack Complex
-Forms a hole in the target cell
-Electrolytes leak out, water flows in rapidly, cell ruptures
95
What are the two protective responses by the second line of defense, and what do both of these responses do?
1) Fever and inflammation
2) Both slow the spread of infections
96
What elevates body temperature?
Fever
97
What can fevers result from?
Results from trauma, infections, drug reactions, brain tumors, and other causes
98
In what 3 ways are moderate fevers helpful?
1) Promotes interferon activity
2) Elevates metabolic rate and accelerates tissue repair
3) Inhibits reproduction of bacteria and viruses
99
Define inflammation and list it's 3 main purposes
-Defined as a local response to tissue injury, including trauma and infection
-3 purposes:
1) Limits spread of pathogens, then destroys them
2) Removes debris from damaged tissue
3) Initiates tissue repair
100
What are the four cardinal signs of inflammation?
Redness, swelling, heat, pain
101
What are the 3 major processes of inflammation?
1) Mobilization of body defenses: get the leukocytes to site of injury as quick as possible
2) Containment and destruction of pathogens
3) Tissue cleanup and repair
102
What are the 6 steps of the mobilization of defenses?
1) Step 1: Release of inflammatory chemicals such Histamine and other cytokines (from basophils, mast cells, damaged cells, toxins, etc.)
2) Step 2: The chemicals cause Vasodilation, which increases blood flow (local hyperemia)
Hyperemia helps washes toxins and metabolic waste from area
3) Step 3: The chemicals increase capillary permeability; fluid, leukocytes, and plasma proteins leave blood and edema occurs
4) Step 4: Neutrophils leave bloodstream to injury site and accumulate within an hour. Margination and diapedesis occur, and chemotaxis drags things to the site
5) Step 5: Fibrinogen (and other clotting factors) released in interstitial fluid clots to wall off microbes
6) Step 6: Neutrophils murder the pathogens and monocytes help with the cleanup
103
How does hyperemia help during the mobilization of defenses?
It helps wash toxins and metabolic waste from area
104
Describe what causes each of the 4 cardinal signs of inflammation
1) Heat: results from hyperemia
2) Redness: due to hyperemia (and extravasated RBCs)
3) Swelling (edema): due to increased fluid filtration from the capillaries
4) Pain: from direct injury to the nerves, pressure on the nerves from edema, stimulation of pain receptors by prostaglandins, bacterial toxins, and bradykinin
105
Define margination
Selectins cause leukocytes to adhere to blood vessel walls
106
Define diapedesis
Emigraton; leukocytes squeeze between endothelial cells into tissue space
107
How do leukocytes get to the site of an injury?
Chemotaxis
108
Describe how clotting traps pathogens
-Heparin (**) prevents clotting directly at the injury site
-Pathogens are in a fluid pocket surrounded by clot
-Pathogens then attacked by antibodies, phagocytes, and other defenses
109
Describe how neutrophils kill things
-They quickly respond to and kill bacteria through phagocytosis and respiratory burst
-Secrete cytokines for recruitment of macrophages and additional neutrophils
110
__________ and _________ secrete colony-stimulating factor to stimulate leukopoiesis (production of more leukocytes) thereby raising WBC counts in blood
Macrophages and T cells
111
Define macrophages, describe what they do, and how long they take to get to the site
-Defined as the primary agents of tissue cleanup and repair; they engulf and destroy bacteria, damaged host cells, and dead and dying neutrophils
-Arrive in 8 to 12 hours and become macrophages
112
What stimulates fibroblasts to multiply and synthesizes collagen during tissue repair?
Platelet-derived growth factor
113
Describe tissue cleanup and repair; what factors are involved?
-Monocytes/ macrophages are the primary agents of cleanup & repair
-Edema forces more fluid into the lymphatic system
-Platelet-derived growth factor stimulates fibroblasts to multiply & synthesizes collagen
-Hyperemia delivers oxygen, amino acids, and other necessities for protein synthesis
-Increased heat increases metabolic rate, speeds mitosis, and tissue repair
-Fibrin clot forms a scaffold for tissue reconstruction
114
What 3 characteristics distinguish adaptive immunity from innate immunity? Describe them
1) Systemic effect: throughout the body
2) Specificity: immunity directed against a particular pathogen
3) Memory: when reexposed to the same pathogen, the body reacts so quickly that there is no noticeable illness
115
What are the 2 forms of adaptive immunity?
1) Cellular (cell-mediated) immunity
2) Humoral (antibody-mediated) immunity
116
In general, what happens during cellular (cell-mediated) immunity?
-T-Cells directly attack and destroy foreign cells or diseased host cells
-Gets rid of intracellular pathogens by killing the cell
117
In general, what happens during humoral (antibody-mediated) immunity?
-B-Cells → plasma cell → antibodies
-Antibodies do not directly destroy a pathogen but tag it for destruction
-Works on extracellular stages of infections
118
Describe the difference between natural and artificially active immunity
1) Natural active immunity: Production of one’s own antibodies or T cells as a result of infection or natural exposure to antigen
2) Artificial active immunity: Production of one’s own antibodies or T cells as a result of vaccination against disease
119
Define a vaccine
Consists of dead or attenuated (weakened) pathogens that stimulate the immune response without causing the disease
120
Define a booster shot
periodic immunizations to stimulate immune memory to maintain a high level of protection
121
Describe the differences between natural passive immunity and artificial passive immunity. Give examples of both
1) Natural passive immunity : Temporary immunity that results from antibodies produced by another person
-Ex: Fetus acquires antibodies from mother through placenta, breast milk after birth
2) Artificial passive immunity: Temporary immunity that results from the injection of immune serum (antibodies) from another person or animal
-Treatment for snakebite, botulism, rabies, tetanus, and other diseases
122
Treating a snakebite would be an example of what kind of immunity?
Artificial passive immunity
123
Define and describe antigens
-Defined as any molecule that triggers an immune response
-Usually large complex molecules
-Regions of an antigen that stimulate immune response are antigenic determinants (**)
-Have characteristics that enable body to distinguish “self” molecules from foreign ones
124
Define haptens, describe what they do, and give a couple examples
-Too small to be antigenic in themselves, they can trigger an immune response by combining with a host macromolecule and creating a complex that the body recognizes as foreign
-Subsequently, haptens alone may trigger response
-Ex: Cosmetics, detergents, industrial chemicals, poison ivy, animal dander, penicillin
125
What are the 3 major cells of the immune system?
Lymphocytes, macrophages, and dendritic cells
126
What are the 3 classes of lymphocytes?
T Lymphocytes (T cells)
B Lymphocytes (B cells)
Natural Killer (NK) cells (second line of defense)
127
What are the 3 stages of a T-cell's life?
Born in bone barrow
Educated in thymus
Deployed to carry out immune function
128
Describe what T-cells do when they're in the thymus
-Each T cell develops a unique surface antigen receptors that corresponds to a specific antigen
-With receptors, the T cells are now activated: capable of recognizing antigens presented to them
129
Describe the criteria used to test T-cells in the thymus before they're sent out. What percent of T-cells pass?
1) Need to be able to recognize self-antigens
2) Not react to the self-antigen
-Only 1-3% of T cells pass the test
130
Define naive lymphocyte pool
immunocompetent T cells that have not yet encountered foreign antigen
131
Define deployment
Naive T cells leave thymus and colonize lymphatic tissues and organs everywhere in the body
132
What are the 3 stages of life of a B-cell?
Born in red bone marrow
Educated in red bone marrow
Deployed to same lymphatic tissues and organs as T cells
133
T cells cannot recognize antigens on their own, so what is required?
Antigen-presenting cells (APCs) are required
134
Give 4 examples of APCs
Dendritic cells, macrophages, reticular cells, and B cells
135
The function of APCs depends on what?
major histocompatibility (MHC) complex proteins
136
Describe what MHC complex proteins do
-Act as cell “identification tags” that label every cell of your body as belonging to you
-Structurally unique for each individual, except for identical twins
137
List and describe the 2 classes of MHC proteins
1) MHC-I proteins
-Produced by nucleated cells
-Will display either normal self-antigens (ignored) or abnormal viral/cancer antigens (attacked)
-Only Cytotoxic T cells respond to MHC-I proteins
2) MHC-II proteins (human leukocyte antigens, HLAs)
-Occur only on APCs and display foreign antigens
-Only Helper T cells respond to MHC-II proteins
138
_________ T-cells respond to MHC-I proteins, whereas ___________ T-cells respond to MHC-II proteins
Cytotoxic T-cells; Helper T-cells
139
Describe the 6 steps of antigen processing
1) APC encounters antigen
2) Internalizes it by endocytosis
3) Digests it into molecular fragments
4) Displays relevant fragments (epitopes) in the grooves of the MHC protein
5) Wandering T cells inspect APCs for displayed antigens
6) If APC only displays a self-antigen, the T cell disregards it; if APC displays a nonself-antigen, the T cell initiates an immune attack
140
Define cellular (cell-mediated) immunity
-Defined as a process in which T lymphocytes directly attack and destroy diseased or foreign cells, and the immune system remembers the antigens and prevents them from causing disease in the future
-Uses 4 classes of T-cells: cytotoxic, helper, regulatory, and memory
141
What 4 classes of T-cells are used on cellular (cell-mediated) immunity?
Cytotoxic, helper, regulatory, and memory
142
What type of T-cell can be described as: “Effectors” of cellular immunity; carry out attack on enemy cells
Cytotoxic T cells (TC), aka killer T cells
143
What type of T-cell helps promote TC cell and B cell action and innate immunity?
Helper T-cells (TH)
144
What type of T-cell can be described as "Inhibits multiplication and cytokine secretion by other T cells; limit immune response"?
Regulatory T cells (TR), aka T-regs
145
What type of T-cell is responsible for memory in cellular immunity?
Memory T-cells (TM)
146
Both cellular and humoral immunity occur in what three stages?
1) Recognition
2) Attack
3) Memory
147
What 2 things make up the process of recognition?
Antigen presentation and T cell activation
148
Describe the process of antigen presentation (4 steps)
1) APC encounters and processes an antigen
2) Migrates to nearest lymph node
3) Displays it to the T cells
4) When T cells encounter a displayed antigen on the MHC protein, they initiate the immune response
149
When does T-cell activation begin?
Begins when TC or TH cell binds to a MHC protein displaying an epitope that the T cell is programmed to recognize
150
Define costimulation and why it's so important
-T cell must be costimulated (aka bind to another APC protein)
- This helps ensure the immune system does not launch an attack in the absence of an enemy; would turn against one’s own body and injure our tissues
151
Successful costimulation will trigger what?
Clonal selection
152
Describe the process of clonal selection (3 steps)
1) Activated T cell undergoes repeated mitosis
2) Produce clones of identical T cells programmed against the same epitope
3) Most cells become effector cells and carry out the attack, while other cells become memory T cells
153
Describe how helper T-cells (TH) help during an attack
When a helper T cell recognizes the Ag-MHC Protein complex, they secrete interleukins which cause:
1) Attract neutrophils and NK cells
2) Attract macrophages, stimulate their phagocytic activity
3) Stimulate T and B cell mitosis and maturation
154
True or false: Helper T cells play central role in coordinating both cellular and humoral immunity
True
155
True or false: Cytotoxic T (𝐓_𝐂) cells are the only T cells that directly attack other cells
True
156
Describe what cytotoxic T (TC) cells do during an attack
1) When the TC cell recognizes complex of antigen and MHC-I protein on a diseased or foreign cell, it “docks” on that cell and it:
a) Releases Perforin and granzymes
b) Interferons and Tumor necrosis factor (TNF)
2) After releasing chemicals, Tc cell goes off in search of another enemy cell.
157
Describe the numerosity and response time of memory T cells (TM)
-Long-lived and more numerous than naive T cells
-Fewer steps to be activated, so they respond more rapidly
158
Describe T cell recall exposure
-Upon re-exposure to same pathogen later in life, memory cells launch a quick attack so that no noticeable illness occurs
-The person is immune to the disease
159
________ immunity is a more indirect method of defense than _______ immunity
Humoral; cellular
160
Summarize humoral immunity in a sentance
B lymphocytes produce antibodies that bind to antigens and tag them for destruction by other means; cellular immunity attacks the enemy cells directly
161
What are the 3 stages of humoral immunity?
Recognition, attack, and memory
162
Describe the recognition phase of humoral immunity
1) An immunocompetent B cell has thousands of surface receptors for one antigen. Activation begins when an antigen binds to several of these receptors, links them together and is taken into the cell by receptor-mediated endocytosis
2) B cell processes (digests) the antigen, links some of the epitopes to its MHC-II proteins, and displays these on the cell surface
3) Helper T cell binds to this Ag–MHC protein complex and secretes interleukins that activate B cell
4) This triggers clonal selection; most differentiate into plasma cells
163
Plasma cells secrete antibodies at a rate of _____ molecules per second during their life span of 4-5 days
2,000; 4-5 days
164
Describe the role of plasma cells in humoral immunity
-First exposure to antigen triggers production of IgM antibodies, later exposures to the same antigen, IgG.
-Antibodies travel through body in blood and other body fluids
165
Describe the attack and memory stages of humoral immunity
1) Attack in humoral immunity: antibodies bind to antigen, render it harmless, “tag it” for destruction
2) Memory in humoral immunity: some B cells differentiate into memory cells
166
Define immunoglobulin (Ig)
An antibody; a defensive gamma globulin found in blood plasma, tissue fluids, body secretions, and some leukocyte membranes
167
The human immune system is capable of as many as _________ different antibodies
1 trillion
168
What are the 5 classes of antibodies?
IgG, IgA, IgM, IgD, IgE
169
List the 5 classes of antibodies in order of abundance
Ig: G, A, M, D, E
170
Describe the IgG antibody class
-80% of total antibodies
-A monomer; most abundant and diverse; crosses placenta to fetus; secreted in secondary immune response; complement fixation
171
Describe the IgA antibody class
-10-15% of total antibodies
-A monomer in plasma; dimer in secretions (mucus, saliva, tears, breast milk, and intestinal secretions – too large to cross placenta)
-Prevents pathogen adherence to epithelia and penetrating underlying tissues
172
Describe the IgM antibody class
-5-10% of total antibodies
-A pentamer; secreted in primary immune response (indicates a current infection); agglutination during ABO incompatibility; complement fixation
173
Describe the IgD antibody class
-0.02% of total antibodies
-A monomer; B cell transmembrane antigen receptor
Thought to function in B cell activation by antigens
174
Describe the IgE antibody class
-0.002% of total antibodies
-A monomer; transmembrane protein on basophils and mast cells causing release of histamine when activated.
175
What are the 4 mechanisms of antibody attack against pathogens? (humoral immunity)
Neutralization, complement fixation, agglutination, and precipitation
176
Describe how neutralization works in humoral immunity attack
Antibodies mask pathogenic region of antigen
177
Describe how complement fixation works in humoral immunity attack
Leads to inflammation, phagocytosis, immune clearance, or cytolysis
178
Describe how agglutination works in humoral immunity attack
-Antibody has 2 to 10 binding sites; binds to multiple enemy cells, immobilizing them from spreading
-Enhances phagocytosis by creating “bigger bites”
179
Describe how precipitation works in humoral immunity attack
-Antibody binds antigen molecules (not cells); creates antigen (an antibody complex that precipitates) allowing them to be removed by immune clearance or phagocytized by eosinophils
180
Define primary immune response
An immune reaction brought about by the first exposure to an antigen
181
Describe how primary immune response works (regarding the humoral memory aspect of it)
-There's a lag period (3-6 days) while naive B cells multiply and differentiate into plasma cells
-As plasma cells produce antibodies, the antibody titer (level in the blood plasma) rises
-IgM appears first, peaks in about 10 days, soon declines
-IgG levels rise as IgM declines, but IgG titer drops to a low level within a month
182
Define the secondary (anamnestic) response in humoral attack
The response if reexposed to the same antigen
183
Describe how secondary (anamnestic) response works (especially regarding the humoral memory aspect)
1) Plasma cells form within hours, not days
2) IgG titer rises sharply and peaks in a few days; response is so rapid that no illness results
3) IgG remain elevated for weeks to years, conferring long-lasting protection, but memory does not last as long in humoral immunity as in cellular immunity
184
True or false: Memory does not last as long in humoral immunity as in cellular immunity
True
185
Name what cellular immunity is best for, what its effector cells are, and how long the memory lasts
Best for: Intracellular pathogens, cancer cells, transplanted tissues
Effector cells: Cytotoxic T cells (helped by Helper T cells)
Memory: usually last life-time
186
Name what humoral immunity is best for, what its effector cells are, and how long the memory lasts
Best for: Extracellular pathogens, toxins, venoms, allergens, mismatched RBCs
Effector cells: Plasma cells (develop from B cells and helped by Helper T cells)
Memory: does not last as long as cellular immunity
187
What is usually the problem in immune disorders?
That immune response is either:
Too vigorous
Too weak
Misdirected against wrong targets
188
Define hypersensitivity and give 3 examples
-Defined as an excessive immune reaction against antigens that most people tolerate
-Ex: Alloimmunity (transplanted tissues), Autoimmunity, and Allergies
189
List and briefly describe the 4 types of hypersensitivity
1) Type I acute (immediate) hypersensitivity
-A very rapid response based on antibodies
2 & 3) Type II and Type III subacute hypersensitivity
-A slower onset (1 to 3 hours after exposure) that lasts longer (10 to 15 hours) and is based on antibodies
4) Type IV: delayed cell-mediated response
-Signs appear 12 to 72 hours after exposure
-Cosmetics, poison ivy, graft rejection, TB skin test
190
Give 4 examples of Type IV sensitivity
Cosmetics, poison ivy, graft rejection, TB skin test
191
Describe type 1 (acute) hypersensitivity. What does it include, and what happens during first and second exposure?
-Includes most common allergies
-The initial contact is asymptomatic but sensitizes person
-A high number of IgE is produced which attaches to basophils and mast cells
-During the second contact with allergen, within seconds, allergen binds to IgE on basophils and mast cells
-This stimulates release of histamine and other inflammatory chemicals
-Usually subsides within 30 minutes, although it can be severe to fatal
192
What are the clinical signs of hypersensitivity?
Local edema, mucus hypersecretion and congestion, watery eyes, runny nose, hives, and sometimes cramps, diarrhea, and vomiting
Examples: food allergies and asthma
193
Define anaphylaxis and how local anaphylaxis can be treated
-An immediate, severe type I reaction
-Local anaphylaxis can be relieved with antihistamines
194
Define and describe anaphylactic shock
-Defined as severe, widespread acute hypersensitivity
-Characterized by bronchoconstriction, dyspnea (labored breathing), widespread vasodilation, circulatory shock, and sometimes death
-Antihistamines are inadequate by themselves
-Epinephrine relieves the symptoms by dilating bronchioles, increasing cardiac output, and restoring blood pressure
-Fluid therapy and respiratory support are sometimes required
195
Define and describe acquired immunodeficiency syndrome (AIDS)
-A group of conditions that severely depress the immune response
-AIDS is caused by infection with the human immunodeficiency virus (HIV)
-Invades helper T cells, macrophages, and dendritic cells by “tricking” them to internalize viruses by receptor-mediated endocytosis
-By destroying TH cells, HIV strikes at the central coordinating agent of innate defense, humoral immunity, and cellular immunity
-Incubation period ranges from several months to 12 years
196
Describe the signs and symptoms of AIDS
-Early symptoms: flu-like symptoms of chills and fever
-Symptoms progresses to night sweats, fatigue, headache, extreme weight loss, lymphadenitis
-Normal TH count is 600 to 1,200 cells/µL of blood, but in AIDS it is less than 200 cells/µL
-Person susceptible to opportunistic infections (Toxoplasma, Pneumocystis, herpes simplex virus, cytomegalovirus, or tuberculosis)
-Candida (thrush): white patches on mucous membranes
-Kaposi sarcoma: cancer originates in endothelial cells of blood vessels; causes purple lesions in skin
197
Describe how AIDS is transmitted
-HIV is transmitted through blood, semen, vaginal secretions, breast milk, or across the placenta
-Most common means of transmission are:
1) Sexual intercourse (vaginal, anal, oral)
2) Contaminated blood products
3) Contaminated needles
-Not transmitted by casual contact
-Undamaged latex condom is an effective barrier to HIV
