Lecture #6: Immunity

Question 1

What are pathogens?

Answer 1

Disease causing agents

Question 2

What do immue systems do?

Answer 2

• recognize foreign cells
• destory pathogens
• produce immue cells and proteins

Question 3

What are the 2 types of immunity?

Answer 3

Innate immunity and adaptive immunity

Question 4

Innate immunity

Answer 4

• present in all animals from time of birth
• an immediate defense upon infection
• responds to broad range of pathogens; non-specific

Question 5

Adaptive immunity

Answer 5

• Present in vertebrates
• develops after exposure to agents such as microbes, toxins, or other foreign substances
• involves a very SPECIFIC response to pathogens

Question 6

Invertebrates

Answer 6

They have INNATE IMMUNITY
- exoskeleton of insects serves as barrier (chitin) to entry
- lysozyme = enzyme that breaks down bacteria cell walls
- itemocytes = cells circulating within hemolyph that carry out phagocytosis
- immue cells recognize bacteria and fungi by structures on their cell walls
- various classes of pathogens elict immune response

Question 7

What is phagocytosis?

Answer 7

Ingestion and digestion of foreign substances including bacteria

Question 8

Vertebrates

Answer 8

THEY HAVE ADAPTIVE IMMUNITY
- Barrier defenses, phagocytosis, antimicrobial peptides (similar to invertebrates)
- Natural killer cells, interferons, inflammatory response (unique to vertebrates)

Question 9

Barrier defenses

Answer 9

• skin and mucous membranes of respiatory, urinary, and reproductive tracts are physical barriers
• mucus traps and allows for the removal of microbes (cilia of respiatory tract)
• many body fluids including saliva, mucus, and tears are hostile to many microbes (lysozomes in respiatory tract and tears)
• The low ph of skin (oil gland secretion) and the digestive system (acidic ph of stomach) prevents growth of many bacteria

Question 10

Cellular innate defenses

Answer 10

• groups of pathogens are recognized by receptors on phagocytic cells
• these receptors recognize fragments of molecules characteristic of a set of pathogens

Question 11

What are the two main phagocytic cells?

Answer 11

• macrophages
• neutrophils

Question 12

What do dendritic cells do?

Answer 12

Stimulates the development of adaptive immunity
- eosinophils discharge destructive enzymes, peptides, and proteins

Question 13

What do peptides and proteins do?

Answer 13

attack pathogens or stop their reproduction

Question 14

Interferon proteins

Answer 14

produced by virally-infected cells warning noninfected cells and activating macrophages

Question 15

Complement system

Answer 15

Consists of about 30 plasma proteins which cause lysis (poke holes) of invading cells
- helps trigger inflammation by attracting phagocytes to the scene

Question 16

Inflammatory response

Answer 16

• mast cells (a type of connective tissue) release histamine which triggers blood vessels to dilate and become more permeable
• activated macrophages and neutrophils release cytokines, signaling molecules that enhance the immune response
• enhanced blood flow to site helps deliver antimicrobial peptides that result in an accumulation of pus (fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues)

Question 17

Inflamation is either…

Answer 17

local: redness, heat, swelling/edema, pain
systemic: throughout the body
- fever is a systemic inflammatory response triggered by pyrogens released by macrophages in response to certain pathogens
- inhibits microbial growth
- speeds up phagocytosis and tissue repair

Question 18

septic shock

Answer 18

life threatening condition caused by overwhelming inflammatory response

Question 19

What does adaptive immunity rely on?

Answer 19

Two types of lymphocytes (type of white blood cell)
- T cells
- B cells

Question 20

T cells

Answer 20

Mature in the thymus

Question 21

B cells

Answer 21

Mature in bone marrow

Question 22

Antigens

Answer 22

substances that can elict a response from a B cell or a T cell
- B cells and T cells bind to antigens via antigen receptors which are specific to part of one molecule of that pathogen
- each individual B or T cell is specialized to recognize a specific type of molecule

Question 23

epitope

Answer 23

small, accessible part of antigen that binds to antigen receptor

Question 24

Antigen recognition by B cells and antibodies

Answer 24

• each b cell antigen receptor is a y-shaped molecule with two identical heavy chains and two identical light chains
• constant regions vary little, variable regions differ greatly
• variable regions provide antigen specificity

Question 25

Antigen recognition by T cells

Answer 25

• T cell receptors have two different polypeptide chains (called α and β)
• Tips of the chain form a variable (v) region, the rest is a constant (c) region
• Bind to antigen fragments displayed/presented on host cell

Question 26

What are the 4 characteristics of the adaptive immune system?

Answer 26

• immense diversity of lymphocytes and receptors
• self- tolerance (lack of reactivity against an animal’s own molecules)
• B + T cells proliferate after activation
• Immunological memory

Question 27

Immunological memory

Answer 27

• responsible for long-term protections against diseases

Question 28

Primary immune response

Answer 28

first exposure to a specific antigen

Question 29

Secondary immune response

Answer 29

memory cells facilitate a faster, more effective response

Question 30

Humoral immune response

Answer 30

antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph (b cells)

Question 31

Cell-mediated immune response

Answer 31

specialized T cells destroy affected host cells (cytotoxic T cells)

Question 32

Helper T cells

Answer 32

type of T cells that triggers both the humoral and cell-mediated immune responses

Question 33

Allergies

Answer 33

exaggerated (hypersensitive) responses to antigens called allergens

Question 34

Autoimmune diseases

Answer 34

the immune system loses tolerance for self, and turns against certain molecules of the body

Question 35

Examples of autoimmune diseases

Answer 35

• Systemic lupus
• erythematosus
• rheumatoid arthritis
• insulin-dependent diabetes mellitus
• multiple sclerosis