7.4 Immune

Question 1

What are the lymphoid tissues?

Answer 1

Bone Marrow: site of white blood cell production
Lymphatic Vessels: carry lymph from tissues to lymph nodes and lymph organs before returning to blood
Lymph Nodes, Tonsils, MALT, appendix: collections of lymphocytes for immune response and macrophages to remove debris
Spleen: replaces worn out blood cells, collections of lymphocytes for immune response and macrophages to remove debris
Thymus: site of T-lymphocyte (T-cell) maturation

Question 2

What are the 3 functions of the lymphatic system?

Answer 2

Immune Support**
Fat Transport (lacteal)
Blood Volume

Question 3

How does lymph return to the heart?

Answer 3

Valves
Milking action of skeletal muscle
Contraction of smooth muscle in vessel walls
Pressure changes in the thorax
Through lymphatic vessels

Question 4

What are lymphocytes?

Answer 4

Naïve lymphocytes circulate through the blood and lymphatic vessels

Lymphocytes that
encounter pathogens
in lymph nodes stop
circulating

Question 5

What are lymph nodes? Where are they located? Fxn?

Answer 5

tiny organs clustered along lymphatic vessels
less than 1inch in length, shaped like a lima bean
Concentrated in the cervical, axillary, and inguinal regions
2 functions:
Filtration: macrophages to clean up debris
Immune activation: lymphocytes to search for pathogens, infection

Question 6

Describe a lymph node

Answer 6

Follicles “slow down traffic”
optimize pathogen lymphocyte interaction
concentrated regions of B-cells and T-cells, also macrophages
become swollen with infection when lymphocytes proliferate

Question 7

What is the function of the tonsil?

Answer 7

Contain lymphocytes that destroy and remove pathogens that enter through air and food

Question 8

Where are tonsils located?

Answer 8

Pharyngeal Tonsils (2) – posterior wall of the nasopharynx
Palatine tonsils (2) – boundary between the soft palate and pharynx
Lingual tonsil – base of tongue

Question 9

How is the appendix important?

Answer 9

contains a high concentration of lymphoid follicles
protect against harmful bacteria in intestines
lymphocyte source for intestines

Question 10

What is the fxn of the spleen?

Answer 10

Contains lymphocytes that initiate immune responses to antigens in the blood (blood borne pathogens)
removes debris and old blood cells and platelets from blood
stores RBC breakdown products
stores platelets and WBC’s

Question 11

Where is the thymus? When is it active? What does it do?

Answer 11

bi-lobed developmentally regulated organ in the mediastinum
Function:
maturation of T-lymphocytes
Most active during childhood, it stops growing during adolescence and then gradually atrophies

Question 12

What is an antigen

Answer 12

are any molecule or partial molecule that can trigger an immune response
= small part of something “other” that our cells recognize

Question 13

What is an immunogen?

Answer 13

an antigen that invokes an immune response

Question 14

What is immunogenicity?

Answer 14

ability to stimulate specific lymphocytes

Question 15

What is a hapten?

Answer 15

foreign protein (carrier) + other molecule 		=basis for allergies
a small molecule antigen that only elicits an immune response when combined with another protein

Question 16

What are the 5 stages of infection?

Answer 16

incubation period: active replication of pathogen, no symptoms (1 day, upto months)
prodromal stage: first symptoms appear, vague sense of illness (malaise, myalgia, headache, fatigue), contagious
acute stage: full infection, rapid proliferation, inflammation, contagious
convalescent stage: resolution and containment begins (days to months)
resolution phase: total elimination of pathogen, signs and symptoms absent

Question 17

What are neutrophils?

Answer 17

50-70% of WBC’s in circulation
first responders to injury, stress, acute inflammation
phagocytic activity
contain lysosomal enzymes to destroy bacteria
release free radicals, can cause injury to surrounding tissue

Question 18

What are monocytes/macrophages? What’s the difference between the two?

Answer 18

monocytes within circulation, become macrophages in tissue
3-7% of WBC’s in circulation
inflammation response, later and more likely in chronic response than neutrophils
phagocytes
engulf, ingest, digest debris and antigens
synthesize and secrete cytokines

Question 19

What are lymphocytes?

Answer 19

B-lymphocytes (B-Cells), T-lymphocytes (T-Cells)
25% of WBC’s in circulation
long term, adaptive immune response
recognize, target, form memory cells for antigens
B-cells: produce antibodies against pathogens
T-cells: target infected and cancerous cells

Question 20

What are basophils?

Answer 20

<1% of WBC’s in circulation
increase in response to infection, primarily parasites
release histamine, heparin, prostaglandins, leukotrienes
assist with recruiting neutrophils

Question 21

What are eosinophils?

Answer 21

2-4% of WBC’s in circulation
release histamine, peroxidase, ribonuclease, deoxyribonuclease, lipase, plasminogens
increase during allergic reactions and parasitic infection

Question 22

What are the innate immune responses?

Answer 22

External Defenses: mechanical, chemical, microbial
Phagocytes
Natural Killer Cells
Interferon
Complement
Fever
Inflammation

Question 23

What are the adaptive immune responses?

Answer 23

Antibody Mediated (Humoral) Immunity
Cell-Mediated (Cellular) Immunity

Question 24

How do mechanical external defenses function?

Answer 24

prevent entry of pathogens into the body
Skin
Fluid: flow of fluid flushes surfaces and body regions to remove pathogens
examples: mucus, urine, sweat, tears
cough & sneeze reflexes propel irritants out

Question 25

How do chemical external defenses work?

Answer 25

Chemical components of the internal epithelial surfaces are present to remove debris and prevent pathogen growth 
Examples
Saliva contains antimicrobial enzymes
Sticky mucus traps particles
Stomach acid kills bacteria
Acidic urine and vaginal secretions prevent bacterial growth
Hair filters particles
Cilia sweeps particles out

Question 26

How do microorganisms contribute to external defenses?

Answer 26

The normal flora, micro-organisms contained on the skin, within the respiratory tract, GI tract, urogenital tract, and eyes
populations of “good” bacteria outcompete “bad” bacteria

Question 27

How to macrophages attract other immune cells?

Answer 27

Release cytokines

Question 28

What are the steps of leukocyte migration to injury?

Answer 28

Migration: cells attracted to site of injury due to inflammatory mediators
Margination: cells move along the wall of the blood vessel
Diapedesis: cells pass through the blood vessels wall to injured tissue
Phagocytosis: cells engulf pathogens and debris at site of injury

Question 29

What are neutral killer cells?

Answer 29

Natural Killer Cells (CD16, CD25) are specialized to nonspecifically detect and destroy virus infected cells and cancerous cells
detect “non self” by looking for cells low in MHC “self” markers

Question 30

What is the mechanism NK cells use? How activated?

Answer 30

release chemicals called perforins that lyse the cell membranes of targets
activated by cytokines

Question 31

What are interferons?

Answer 31

(viruses have nucleic acids, but take over host cells machinery to reproduce)

Host cell 1, with viral infection, signals with INTERFERON to warn nearby cells of viral presence
Interferons trigger enzyme cascades that block viral entry into the next cell; also activate immune system, slows cell division and tumor growth

Question 32

What is the complement system?

Answer 32

attract phagocytes, increase phagocytosis
increase inflammation
forms Membrane attack complex ; large channel in the membrane that disrupts osmotic balance and causes cell to swell and burst

= Compliment or add to phagocytic and antibody response

Question 33

What are 2 ways the complement system can be activated?

Answer 33

lectin-mediated: recognize lectins which bind to sugars on microorganism surface
antibody activation: B-cell mediated response during adaptive immunity