Ch 8 - The Immune System

Question 1

What is the difference between innate and adaptive immunity?

Answer 1

• innate: composed of defenses that are always active, but that cannot target a specific invader and cannot maintain immunologic memory; also called nonspecific immunity
• adaptive: composed of defenses that take time to activate, but that target a specific invader and can maintain immunologic memory; also called specific immunity

Question 2

Where do immune cells (B and T cells) develop, mature, and their major functions?

Answer 2

• both develop in bone marrow
• B cells mature in bone marrow; T cells mature in thymus
• B cells produce antibodies (specific, humoral mediated)
• T cells coordinate immune system and directly kill infected cells (specific, cell mediated)

Question 3

What do lymph nodes do?

Answer 3

• filter lymph

- site where immune responses can be mounted

Question 4

Where is the site of T cell maturaiton?

Answer 4

thymus

Question 5

What does the gut-associated lymphoid tissue (GALT) include?

Answer 5

tonsils and adenoids

Question 6

What role do leukocytes play in in the immune system?

Answer 6

WBC involved in immune defenses

Question 7

What is the skin’s role in the immune system?

Answer 7

acts as a physical barrier and secretes antimicrobial compounds, like defensins

Question 8

What is the mucus’s role in the immune system?

Answer 8

mucus on mucous membranes traps pathogens; in the respiratory system, the mucus is propelled upward by cilia and can be swallowed or expelled

Question 9

What do tears and saliva contain to help the immune system?

Answer 9

lysozyme, an antibacterial compound

Question 10

What is the stomach’s role in the immune system?

Answer 10

• the stomach produces acid, killing most pathogens

- colonization of the gut helps prevent overgrowth by pathogenic bacteria through composition

Question 11

What is the complement system’s role in the immune system?

Answer 11

can punch holes in the cell walls of bacteria, making them osmotically unstable

Question 12

What is the interferons role in the immune system?

Answer 12

given off by virally infected cells and help prevent viral replication and dispersion to nearby cells

Question 13

What is the macrophages role in the immune system?

Answer 13

• they ingest pathogens and present them on major histocompatibility complex (MHC) molecules
• they also secrete cytokines

Question 14

What is the difference between MHC-I and MHC-II?

Answer 14

• 1: present in all nucleated cells and displays endogenous antigen (proteins from within the cells) to cytotoxic T cells (CD8+ cells) allowing the detection of cells infected with intracellular pathogens (especially viruses)
  2: present in professional antigen-presenting cells (macrophages, dendritic cells, some B cells, and certain activated epithelial cells) and displays exogenous antigen (proteins from outside the cell) to helper T cells (CD4+ cells)

Question 15

What are dendritic cells?

Answer 15

antigen-presenting cells in the skin
- it presents antigens, fragments of protein or other molecules from pathogens or cancer cells, to adaptive immune cells, inducing them to attack bearers of the displayed antigen

Question 16

What is the natural killer cells role in the immune system?

Answer 16

attack cells not presenting MHC molecules (healthy cells exhibit MHC 1 class molecules), including virally infected cells and cancer cells

Question 17

What are granulocytes and their role in the immune system?

Answer 17

• neutrophils: ingest bacteria, particularly opsonized bacteria (those marked with antibodies); can follow bacteria using chemotaxis
• eosinophils: used in allergic reactions and invasive parasitic infections; release histamine, causing an inflammatory response
• basophils: used in allergic reactions; mast cells are related cells found in skin

Question 18

What is humoral immunity?

Answer 18

centered on antibody production by plasma cells, which are activated by B cells (antigens stimulate this cell to divide and produce antibodies that neutralize invaders or tag them for killing)

Question 19

What do antibodies target and what do they contain in humoral immunity?

Answer 19

• target a particular antigen
• contain 2 heavy chains and 2 light chains
• have a constant region and a variable region; the tip of the variable region is the antigen-binding region

Question 20

What happens when the antigen-binding region is activated in humoral immunity?

Answer 20

• they undergo hypermutation to improve the specificity of the antibody produced
• cells may be given signals to switch isotypes of antibody (IgM, IgD, IgG, IgE, IgA)

Question 21

What does circulating antibodies do in humoral immunity?

Answer 21

• can opsonize pathogens (mark them from destruction)
• cause agglutination (clumping) into insoluble complexes that are ingested by phagocytes
• neutralize pathogens

Question 22

What are cell-surface antibodies capable of in humoral immunity?

Answer 22

activating immune cells or mediating allergic reactions

Question 23

What do memory B cells do?

Answer 23

lie in wait for a second exposure to a pathogen and can then mount a more rapid and vigorous immune response (secondary response)

Question 24

What is cell-mediated (cytotoxic) immunity?

Answer 24

centered on the functions of T cells (A killer T cell destroys an infected cell in which it detects the presence of antigens; other T cells (helper/regulatory) coordinate immune response

Question 25

How do T cells undergo maturation in the thymus in cell mediated immunity?

Answer 25

through positive selection (only selecting for T cells that can react to antigen presented on MHC) and negative selection (causing apoptosis in self reactive T cells)

Question 26

What peptide hormone promotes T cell development?

Answer 26

thymosin

Question 27

What is the role of helper T cells in cell mediated immunity?

Answer 27

- (Th or CD4+) respond to antigen on MHC-II and coordinate the rest of the immune system, secreting lymphokines to activate various arms of immune defense

Question 28

What is the difference between Th1 and Th2 cells?

Answer 28

- 1: secrete interferon gamma, which activates macrophages | - 2: activates B cells, primarily in parasitic infections

Question 29

What is the role of cytotoxic T cells (Tc, CTL, or CD8+) in cell mediated immunity?

Answer 29

respond to antigen on MHC-I and kill virally infected cells

Question 30

What is the role of suppressor T cells (Treg) in cell mediated immunity?

Answer 30

tone down the immune response after an infection and promote self tolerance

Question 31

What is the role of memory T cells in cell mediated immunity?

Answer 31

serve a similar function to memory B cells in allowing a more rapid response after second exposure to a pathogen

Question 32

What is a self-antigen identified as in autoimmune conditions?

Answer 32

a foreign, and the immune system attacks the body's own cells

Question 33

What incites an inflammatory response in allergic reactions?

Answer 33

nonthreatening exposures

Question 34

What is immunization?

Answer 34

a method of inducing active immunity (activation of B cells that produce antibodies to an antigen) prior to exposure to a particular pathogen

Question 35

What is the lymphatic system?

Answer 35

- a circulatory system that consists of one way vessels with intermittent lymph nodes - equalizes fluid distribution, transports fats and fat-soluble compounds in chylomicrons, and provides sites for mounting immune responses

Question 36

How does the lymphatic system connect the cardiovascular system?

Answer 36

via the thoracic duct in the posterior chest

Question 37

What does the spleen do?

Answer 37

acts as a storage area for WBCs and plts, a recycling center for RBCs, and a filter of blood and lymph for the immune system - location where B cells mature and proliferate

Question 38

Which cells are agranulocytes?

Answer 38

lymphocytes (T and B cells) and monocytes (macrophages)

Question 39

How are MHC molecules joined? What is it's path once joined?

Answer 39

- joined by antigens - MHC-antigen complex then goes to the cell surface to display the antigen allowing the immune system to monitor the health of cells

Question 40

Why is it important to match MHC types of donors to recipients during transplants?

Answer 40

- to avoid rejection - MHC molecules are highly variable but can be divided into particular subtypes that have different susceptibility to diseases

Question 41

What are the innate immune cells?

Answer 41

non specific and form the first line of defense against pathogens - macrophages, mast cells, granulocytes, dendritic cells, and natural killer cell

Question 42

What do mast cells do?

Answer 42

releases histamine and other chemicals that promote inflammation

Question 43

What does histamine do?

Answer 43

causes inflammation by inducing vasodilation and the movement of fluid and cells from the bloodstream into tissues

Question 44

How do CD4+ T cells compare to CD8+ T cells?

Answer 44

- 4 are better at fighting extracellular infections; respond to MHC-II (4 x2 = 8) - 8 are better at targeting intracellular infections; respond to MHC-I (8 x 1 = 8)

Question 45

What are plasma cells?

Answer 45

form from B cells exposed to antigen and produce antibodies

Question 46

How do antibodies become specific for a given antigen?

Answer 46

- B cells originally mature in the BM and have some specificity at that point; however, antibodies that can respond to a given antigen undergo hypermutation, or rapid mutation of their antigen-binding sites - only those B cells that have the highest affinity for the antigen survive and proliferate, increasing the specificity for the antigen over time

Question 47

What is the difference between passive and active immunity?

Answer 47

- active: the stimulation of the immune system to produce antibodies against a pathogen (requires weeks to build) - passive: the transfer of antibodies to prevent infection, without stimulation of the plasma cells that produce these antibodies (acquired immediately)