Immune System

Question 1

Pathogens

Answer 1

■ Microscopic organisms that cause disease:
o viruses
o bacteria
o fungi
o parasites
■ nEach attacks in a specific way

Question 2

Body defenses

Answer 2

■ Provide resistance to fight infection, illness, and disease
■ 2 categories of defenses:
■ nonspecific (innate) defenses
■ specific (adaptive) defenses

Question 3

Nonspecific defenses

Answer 3

■ Always work the same way
■ Against any type of pathogen agent

Question 4

7 types of nonspecific resistance

Answer 4

1. Physical barriers
2. Phagocytic cells
3. Immunological surveillance
4. Interferons
5. Complement
6. Inflammation
7. Fever

Question 5

Specific defenses

Answer 5

■ Protect against specific pathogens
■ Depend on activities of lymphocytes
■ Specific resistance (immunity):
■ develops after exposure to environmental hazards

Question 6

Nonspecific and specific defenses

Answer 6

Operate together to provide resistance to infection and disease

Question 7

7 nonspecific defenses: physical barriers

Answer 7

■ Keep hazardous materials outside the body
■ Outer layer of skin
■ Hair
■ Epithelial layers of internal
passageways – Mucous Membranes

■ Secretions that flush away materials:
■ sweat glands, mucus, and urine
■ Secretions that kill or inhibit microorganisms:
■ enzymes, antibodies, acidity of skin and stomach acid

■ Respiratory system modifications
■ Mucus-coated hairs in nose
■ Cilia of upper respiratory tract sweep dust- and bacteria-laden mucus toward mouth

■ Surface barriers breached by nicks or cuts - second line of defense must protect deeper tissues

Question 8

Phagocytes

Answer 8

■ Attack and remove dangerous microorganisms
■ First line of cellular defense

Question 9

2classes of phagocytes

Answer 9

■ Microphages:
■ neutrophils and eosinophils

■ Macrophages:
■ large phagocytic cells derived from monocytes

Question 10

2 types of macrophages

Answer 10

■ Fixed macrophages
■ Free (wandering) macrophages

Question 11

Fixed macrophages

Answer 11

■ Also called histiocytes
■ Stay in specific tissues or organs:
■ e.g., dermis and bone marrow

Question 12

Specific Histiocytes

Answer 12

■ Microglia:
■ found in central nervous system

■ Kupffer cells:
■ found in liver sinusoids

Question 13

Free (wandering) macrophages

Answer 13

■ Travel through blood stream
■ Special free macrophages:
■ alveolar macrophages (phagocytic dust cells)

Question 14

3 functional characteristics of free macrophages and mircophages

Answer 14

■ Emigration – the ability to move through capillary walls
■ Chemotaxis – They are attracted or repelled by chemicals in surrounding fluids
■ Cytokines

■ Adhesion - phagocytosis begins:
■ when phagocyte attaches to target adhesion
■ Some microorganisms evade adherence with capsule

Question 15

NK cell function

Answer 15

■ Identifies and attaches to abnormal cell (non-selective)
■ without the “self” cell surface protein markers
■ Antibody coating target cell
■ or with abnormal markers

■ Induce apoptosis in cancer cells, foreign and virus-infected cells
■ Secrete potent chemicals that enhance inflammatory response

Question 16

Interferons

Answer 16

■ Proteins (cytokines) released by activated lymphocytes, macrophages and virus-infected cells
Cytokines
■ Chemical messengers released by tissue cells:
■ to coordinate local activities

■ Can trigger production of antiviral proteins in surrounding normal cells

■ Antiviral proteins:
■ do not kill viruses
■ block replication in cell

Question 17

3types of interferons

Answer 17

■ Alpha and Beta interferons:
■ produced by leukocytes
■ Also attract and stimulate NK cells

■ Gamma interferons:
■ secreted by T cells and NK cells
■ Widespread immune mobilizing effects
■ stimulate macrophage activity

■ Since IFNs activate NK cells and macrophages, indirectly fight cancer
■ Artificial IFNs used to treat hepatitis C, genital warts, multiple sclerosis, hairy cell leukemia

Question 18

Complement

Answer 18

■ Plasma contains ~ 20 complement (C) proteins:
■ that complement antibody action

■ Include C1–C9, factors B, D, and P, and regulatory proteins
■ Major mechanism for destroying foreign substances
■ Our cells contain complement activation inhibitors

Question 19

Complement (C) proteins

Answer 19

■ Form the complement system
■ Complements action of antibodies

Question 20

Complement activation

Answer 20

■ Enhances both innate and adaptive defense

■ 3 pathways activate the complement system
■ classical pathway
■ alternative pathway
■ Lectin pathwa

Question 21

Classical pathway

Answer 21

■ Fast method
■ C1 binds to or is fixed to antibody molecule attached to antigen (bacterium)

■ Bound (fixed) protein acts as enzyme:
■ catalyzes chemical reaction between other C proteins

Question 22

Alternative pathway

Answer 22

■ Slow method (No antibody involved)

■ Involves the exposure to antigen on the surface of a microbe :
■ factor P (properdin)
■ factor B
■ and factor D interact in plasma

Question 23

Lectin pathway

Answer 23

■ Slow method (also no antibody involved)

■ After digesting microbes, macrophages release substances that:
■ Cause the liver to produce lectins
■ Lectins bind to microbes causing the activation of C3

Question 24

Complement Activation

Answer 24

■ All 3 pathways end with:
■ conversion of inactive complement protein (C3)
■ to active form (C3a + C3b)

Question 25

4 effects of complement activation

Answer 25

1. Stimulation of inflammation - stimulates histamine release
2. Promoting chemotaxis - Attraction of phagocytes to areas of pathogen through chemical signals
   -increases the number of leukocytes in a tissue
3. Opsonization
   ▪ Enhancement of phagocytosis by :
   ■ complements working with antibodies (opsonins) to coat pathogens and make it easier for macrophages to bind
4. Destruction of target cell pathogens (lysis):
   ■ 5 complement proteins join to form membrane attack complex (MAC)

Question 26

Inflammation

Answer 26

■ Also called inflammatory response
■ A biological response
■ Triggered by any stimulus that kills cells or injures tissue

■ Begins with chemicals released into ECF by injured tissues, immune cells, blood proteins
■ Macrophages and epithelial cells of boundary tissues bear Toll-like receptors (TLRs)
■ 11 types of TLRs recognize specific classes of infecting microbes
■ Activated TLRs trigger release of cytokines that promote inflammation

Question 27

Cardinal signs and symptoms of inflammation

Answer 27

■ Swelling (tumor)
■ Redness (rubor)
■ Heat (calor)
■ Pain (dolor)

Question 28

4 Effects of inflammation

Answer 28

1. Temporary repair and barrier against bacteria
2. Retards spread of pathogens into surrounding areas
3. Mobilization of local and systemic defenses:
   ■ and facilitation of repairs (regeneration)
4. Alerts adaptive immune system

Question 29

Injured cells release:

Answer 29

■ prostaglandins
■ proteins
■ potassium ions

Question 30

Products of inflammation

Answer 30

■ Necrosis:
■ local tissue destruction in area of injury
■ Pus:
■ mixture of debris and necrotic tissue
■ Abscess:
■ pus accumulated in an enclosed space

Question 31

Fever

Answer 31

■ A high body temperature:
■ increases body metabolism
■ accelerates HR, respiratory function, protein use, immune function, and mental processing
■ inhibits some viruses and bacteria
■ Causes liver and spleen to sequester iron and zinc (needed by microorganisms)

■ A maintained body temperature above 37°C (99°F)