The Human Immune System

Question 1

~First line of nonspecific defense

Answer 1

● Barrier that helps prevent pathogens from entering the body

Question 2

~Pathogens

Answer 2

● Things that cause disease

Question 3

~Second line of nonspecific defense

Answer 3

● Menat to limit the spread of invaders in advance of specific immune responses
● Microbes that get into the body encounter this

Question 4

~Histamine

Answer 4

● Triggers vasodilation that increases blood supply to the area, bringing more phagocytes
● Secreted by basophils and mast cells, found in the connective tissue
● Responsible for the symptoms of the common cold: sneezing, coughing, redness, itchy eyes, and runny nose

Question 5

~Vasodilation

Answer 5

● Enlargement of blood vessels

Question 6

~Basophils

Answer 6

● A type of circulating white blood cell

Question 7

~Prostaglandins

Answer 7

● Further promote blood flow tot he area

Question 8

~Chemokines

Answer 8

● Secreted by blood vessel endothelium and monocytes

● Also attract phagocytes to the area

Question 9

~Pyrogens

Answer 9

● Released by certain leukocytes

● Increase body temperature to speed up the immune system and make it more difficult for microbes to function

Question 10

~Phagocytes

Answer 10

● Ingest invading fungal and bacterial microbes
● Two types: neutrophils and macrophages
● Migrate to an infected site in response to local chemical attractants
● Response is called chemotaxis

Question 11

~Neutrophils

Answer 11

● Engulf microbes and die within a few days

Question 12

~Monocytes

Answer 12

● Transform into macrophages
● Extend pseudopods
● Engulf huge numbers of microbes over a long period of time
● Digest hte microbes with a combination of lysozyme nad two toxic forms of oxygen: superoxide anion and nitric oxide

Question 13

~Complement

Answer 13

● A group of proteins

● Leads ot the lysis (bursting) of invading cells

Question 14

~Interferons

Answer 14

● Block cell-to-cell viral infections

Question 15

~Natural killer (NK) cells

Answer 15

● Destroy virus-infected body cells (as well as cancerous cells)
● Attack the cell membrane, causing it to lyse and die

Question 16

~Adaptive third line of defense

Answer 16

● Relies on B lymphocytes and T lymphocytes, hwich arise from stem cells in bone marrow
● Once mature, both cell types circulat ein the blood, lymph, and lymphatic tissue (spleen, lymph nodes, tonsils, and adenoids)
● Both cell types recognize different specific antigens

Question 17

~Recognition

Answer 17

● Antigen receptors on B and T lymphocytes recognize specific antigens or epitopes by binding to them
● In order to recognize an antigen, it must be presented to a B or T cell by an antigen-presenting cell

Question 18

~Antigens

Answer 18

● Any substance that elicits an immune response from B cell or T cells

Question 19

~Epitopes

Answer 19

● An accessible piece of an antigen that elicits an immune response from a B or T cell
● Each B cell displays specificity for one particular epitope

Question 20

~Activation Phase

Answer 20

● The binding of an antien receptor activates B and T cells, causing them to undergo rapid cell division
● The cell form populations of effector cells and memory cells

Question 21

~Effector phase

Answer 21

● After being activated, B cells produce a humoral response
- They produce anitibodies
● T cells engage in a cell-mediated response

Question 22

~Cell-mediated immune response

Answer 22

● Begins when T cell antigen receptors recognize and bind to antigens that display on the surface of antigen-presenting cells (APCs) by a molecule called MHC

Question 23

~Major histocompatibility complex (MHC)/Human leukocyte antigens (HLA)

Answer 23

● Collection of cell surface markers that identify the cells as self
● No two people, except identical twins, have the same MHC markers
● Class I and Class II
● APCs have both MHCI and MHCII on the cell surface

Question 24

~Memory cells

Answer 24

● Cells that can rapidly respond to any exposure to the same antigen many eyars later
● Responsible for immunological memory
● Remain in the body for the rest of one’s life and can rapidly respond to any future exposure to the same antigen

Question 25

~T cells

Answer 25

● Form in bone marro | ● Mature in the thymus gland

Question 26

~Helper T cells/CD4 cells

Answer 26

● Are activated by an interaction with an APC ● Once activated, Helper T cells announce to the immune system that foreign antigens have entered hte body ● Trigger both humoral and cell-mediated immune response ● Activate other Helpter T cells and cytotoxic T cells and B cells by releasing cytokines, interleukin-1 (Il-1) and interleukin-2 (Il-2) ● Targeted by HIV

Question 27

~Cytotoxic T cells/Killer T cells/CD8 cells

Answer 27

● Activated by helper T cells ● Kill body cells infected with pathogens as well as cancer cells ● Cell-mediated immune response ● Proliferates and differentiates into an effector cell and a memory cell ● Activated Cytotoxic T cells attack and kill infected cells by releasing perforin, granzymes that cause the cell to lyse and die ● Infecting microbes are released into the blood or tissue and are disposed of by circulating antibodies

Question 28

~Perforin

Answer 28

● A protein that forms pores in the target cell's membrane

Question 29

~Granzymes

Answer 29

● Enzymes that break down proteins

Question 30

~B cells

Answer 30

● Mature in bone marrow ● A typical B lymphocyte or B cell has about 100,000 identical antigen receptors on its surface that it sues to recognize pathogens ● Every B cell has a differnet antigen receptor

Question 31

~Antigen receptor on B cell

Answer 31

● Y-shaped molecule consisting of 4 polypeptide chains: 2 identical heavy chains and 2 identical light chains ● Each chain has constant and variable regions ● Antibodies secreted by B cells are soluble forms of these antigen receptors

Question 32

~Humoral immune response

Answer 32

● Produce antibodies (immunoglobins) ● When they beocme activated, B cells secrete about 2000 antibodies per second over the cell's 4-5 day life span ● B cell becomes activated when an APC presents an antigen or epitope on its cell surface using a class II MHC molecule ● A helper T cell that recognizes thies epitope-MHC moleucle complex is activated with the aid of cytokines secreted from the APC ● The B cell undergoes multiple cell division once activated

Question 33

~Effector cells/Plasma cells (B)

Answer 33

● Secrete antibodies ● The effector cells are short-lived and begin battle immediately - Neutralize or destroy all of those idntified antigens and any pathogen that produces them

Question 34

~Self-tolerance

Answer 34

● The immune system exhibits this | ● Does not attack body cells

Question 35

~Autoimmune disease

Answer 35

● Somtimes immature lymphocytes develop that have antigen receptors specific for hte body's own cells - If allowed to escape, these cells oudl attackthe body's cells ● The system cannot properly distringuish between self and nonself

Question 36

~Self-reactivity

Answer 36

● To avoid autoimmune disease, lymphocytes are tested for self-reactivity as they mature in the bone marrow ● B and T cells that are idntified as self-reactive are destroyed by apoptosis

Question 37

~Apoptosis

Answer 37

● Programmed cell death

Question 38

~Regulatory T cells

Answer 38

● Inhibit the activation of the immune system in response to self-antigens ● Secrete interleukin-10 (Il-10)

Question 39

~Class I MHC molecuels

Answer 39

● Found on the surfaces of every nucleated body cells

Question 40

~Class II MHC molecules

Answer 40

● Found on specialized cells, including macrophages, B cells, dendritic cells, and activated T cells

Question 41

~Antigen-presenting cells (APCs)

Answer 41

● Present an antigen or piece of an antigen, an epitope, to the immune system ● Begins when an APC (macrophage, dendritic cell or B cell) takes in an antigen ● Either hte APC becomes infected witht he antigen or engulfs it

Question 42

~Clonal selection

Answer 42

● One particular lymphocyte that matches a specific antigen or epitope, called antigenic determinant, is identified and activated ● Once activated, the lymphocyte divide rapidly, forming a population of clones that develop into effector and memory cells ● The effector cells are short-lived and begin battle immediately ● The remaining clones develop into long-term memory cells

Question 43

~Antibodies/immunoglobins

Answer 43

● A group of globular proteins ● Each antibody molecule is a Y-shaped molecule consisting of four popypeptide chians (2 heavy, 2 light, joined by disulfide bridges) ● Consists of four unchanging or constant regions (C) and four variable regions (V) ● Tips of the Y have specific shapes and are htebinding sites for different antigens ● Chosedn by clonal selection

Question 44

~Immunological memory

Answer 44

● The second exposure is more rapid and more intense than the primary immune response

Question 45

~Passive immunity

Answer 45

● Temporary ● Antibodies are transferred to an individual from someone else ● Ex) maternal antibodies that pass through the placenta tot he developing fetus or through breast milk to the baby ● Ex) A person with a weak immune system oftern receives an injection of gamma globulin (IgG), which are antibodies culled from many people, to boost the weak immune system

Question 46

~Active immunity

Answer 46

● Permanent ● The individual makes his/her own antibodies after being ill nad recovering or after being given an immunization or vaccine

Question 47

~Vaccine

Answer 47

● Contains dead or live viruses or enough of the outer coat of a virus to stimulate a full immune response and to impart lifelong immunity

Question 48

~Transfusion reaction

Answer 48

● GIving the wrong blood type to someone can cuase a transfusion reaction or even death ● COmes if the recipient has antibodies to the donor's antigens

Question 49

~Cross-match

Answer 49

● Before someone receives a transfusion of blood, two samples of donor and recipient blood must be mixed to determine compatibility

Question 50

~Universal donor

Answer 50

● Blood type O | ● No blood cell antigens to be clumped by the recipient's blood

Question 51

~Universal recipient

Answer 51

● Blood type AB | ● No antibodies to clump thedonor's blood

Question 52

~Rh factor

Answer 52

● Another antigen located on the surface of red blood cells ● Most of the population (85%) has the antigen and are called Rh+ ● THose without the antigen (15%) are Rh-

Question 53

~AIDS

Answer 53

● Acquired immune deficiency disease ● Highly susceptible to opportunistic diseases, infections, and cancers that take advantage of a collapsed immune system ● HIV causes AIDS, attacks cells that bear CD4 molecules ont heir surface, mainly helpter T cells

Question 54

~HIV

Answer 54

● Human immunodeficiency virus ● Retrovirus ● Once inside a cell, it reverse transcribes itself, using the enzyme reverse transcriptase, and integrates the newly formed DNA intot he host cell genome ● Reminas in the nucleus as a provirus, directing the production of new viruses

Question 55

~Positive feedback

Answer 55

● Enhances an already existing process until some endpoint or maximum rate is reached ● Ex) When a helper T cell becomes activated by a MHCII molecule, it releases two cytokines, Il-1 and Il-2 - Il-2 stimualtes B cells and other T cells into action - Il-1 enhaces hte activity of the already activated helper T cells, stimulating them more until they are activated to a maximum

Question 56

~Negative feedback

Answer 56

● A means to achieve stability

Question 57

~Allergies

Answer 57

● Hypersensitve immuner esponses to certain substances called allergens ● Involve the release of histamine, an anti-inflammatory agent, which causes blood veessesl to dilate ● Normal reaciton involves redness, runny nose, and itchy eyes

Question 58

~Antihistamines

Answer 58

● Can normally counteract the symptoms of allergies

Question 59

~Anaphylactic shock

Answer 59

● An acute allergic response can result in a life-threatening response ● Cn aresult in death within minutes

Question 60

~Antibiotics

Answer 60

● Medicines that kill bacteria or fungi | ● Where vaccines are given to prevent illness caused by viruses, antibiotics are administered after a person is sick

Question 61

~Autoimmune disease Example

Answer 61

● Multiple sclerosis ● Lupus ● Arthritis ● juvenile diabetes

Question 62

~Multiple sclerosis

Answer 62

● The immune system attacks the myelin sheath surrounding certain neurons in the CNS

Question 63

~Monoclonal antibodies

Answer 63

● Antibodies produced by a single B cell that have been selected because they produce one specific antibody ● Important in research and in the treatment and diagnosis of certain diseases

Question 64

~Specificity

Answer 64

● The entire system depends ont he matching of antigens to antigen receptors and hte matching of antigens to antibodies

Question 65

~Diversity

Answer 65

● A wide variety of different cell types defend our bodeies from pathogens

Question 66

~Memory cells

Answer 66

● B and T memory cells circulate for a lifetime

Question 67

~Capacity to distinguish self form nonself

Answer 67

● Most of hte time, the immune system doesnot attack healthy body cells (self-tolerance)

Question 68

~What does the first line of nonspecific defense include?

Answer 68

● Skin ● Mucous membranes, which release mucus that contains antimicrobial substances including lysozyme ● Cilia in the respiratory system to sweep out mucus with its trapped microbes ● Stomach acid

Question 69

~What does the second line of nonspecific defense include?

Answer 69

``` ● Inflammatory response - Histamine - Prostaglandins - Chemokines - pyrogens ● Phagocytes ● Complement ● Interferons ● Natural killer (NK) cells ```

Question 70

~What are the three stages of adaptive immune response?

Answer 70

● Recognition ● Activation phase ● Effector phase

Question 71

~How do APCs break apart antigen once they are inside the host?

Answer 71

● Enzymes break apart the antigen into fragments and attach them to an MHC molecule int he cytoplasm ● The MHC molecule, with the antigen fragment attached, then moves to the surface of hte cell and displays it ● Other cells of the immune system, such as T cells or other B cells, become activated if they can properly bind with the exposed antigen

Question 72

~What are the four characteristics of the immune system?

Answer 72

● Specificity ● Diveristy ● Memory ● Capacity to distinguish self from nonself