Chapter 24: Immune System

Question 1

Compare and contrast innate and adaptive immune systems

Answer 1

Innate:
* Non-specific
* Present since birth
* Fast-acting

Adaptive:
* Specific
* Slow
* Develops after birth, needs to be activated by specific pathogen

Question 2

What is the function of the lymphatic system?

Answer 2

Lymphatic vessels transport fat and return fluid from tissue to the circulatory system thru subclavian veins.

Question 3

Function of lymphatic organs and lymph nodes.

Answer 3

Macrophages and lymphocytes (activate adaptive immue response) residing in * filter circulating lymph that contain microbes and toxins.

Question 4

List the components of innate immunity (internal and external).

Answer 4

External:
Physical barriers e.g. skin, cilia, stomach acid.
Internal:
1. Phagocytic cells (neutrophils and macrophages).
1. Natural killer cells (lymphocytes) attack our own cells that are infected (cancer and virus-infected cells).
1. Basophils and mast cells release histamine when activated.
1. Eosinophils kill parasites.
1. Defensive proteins (e.g. interferons and complement proteins).

Question 5

Describe the inflammatory response

Answer 5

When tissue is damaged:
1. Mast cells and macrophages in tissue release chemical signals (histamines and cytokines) that cause nearby capillaries to dilate and become more permeable.
2. Neutrophils in blood migrate to site of injury and digest bacteria and cell debris.

This causes swelling, increased heat, pain, redness.

Question 6

Diff between localized and systemic response

Answer 6

Localized:
* Limits further infection. If infection spreads, body will react

Systemically:
* Fever: cytokines cause increase in body temp. - inhibits pathogen growth and increases responsiveness of some leukocytes.
* Septic shock: bad inflammatory response to infection - vasodilation causes uneven blood supply throughout body = decrease blood pressure, possible organ failure and death.

Question 7

What are antibodies? What is the general structure of antibodies?

Answer 7

A protein produced by immune system in response to an antigen.
* Has antigen-binding site specific to an antigen.

Question 8

Function of antibodies

Answer 8

• Tags antigen for removal and neutralizes antigen, enhancing phagocytosis.
• Activates complement system, leading to cell lysis somehow.

Question 9

List and describe the four key features of adaptive immunity

Answer 9

Specific: acts against specific pathogen based on antigen present on pathogen.
Diversity: large # of lymphocytes that each respond to specific pathogen.
Memory: recognizes previously encountered antigens.
Non-celf recognition: lymphocytes that recognize “self-antigen” are eliminated.

Question 10

Compare and contrast (adpative) active and passive immunity

Answer 10

Active:
* Lifelong.
* Acquired by recovery from disease.
* Acquired artificially with vaccines.

Passive:
* Temporary
* Involves transfer of antibodies (e.g. from mother to fetus thru placenta or thru breastmilk, thru antibody injections).

Question 11

Compare and contrast humoral and cell-mediated immunity

Answer 11

Humoral:
* Happens in body fluids
* Involves B cells that make free-floating antibodies that bind to extracellular antigens.

Cell-mediated:
* Happens in infected cells
* Involves T cells that bind to antigen-presenting cells and kill infected cells .

Question 12

What are helper T cells? What do signalling proteins do?

Answer 12

Helper T cells recognize antigen-presenting cells like macrophages and B cells. Once activated, they secrete signalling proteins that
1. Make helper T cells grow and divide
2. Stimulate activity of cytotoxic T cells.
3. Activate B cells → stimulates humoral immunity.

Question 13

How do B and T cells recognize antigens? What is clonal selection?

Answer 13

They have antigen receptor proteins on the surface cell. Antigens activates lymphocytes that have complementary antigen receptors. Activated lymphocytes go thru clonal selection to differentiate and divide into effector cells and memory cells.

Question 14

What are antigen-presenting cells (macrophages)?

Answer 14

E.g. macrophages and B cells. Macrophages engulf pathogens and display antigens to other immune cells.

Question 15

What are memory cells and effector cells?
What are their functions?
Give examples.

Answer 15

Effector cells:
* Short-lived, fast acting
* Carry out immune response by destroying or inactivating antigens.
* effector B cells (plasma cells) secrete antibodies
* effector cytotoxic T cells kill targeted cells.

Memory cells
* Long-lasting, remain in lymph. system.
* Don’t actively participate in initial immune response.
* In subsequent encounters, will trigger faster reaction.

Question 16

Contrast the primary and secondary immune response

Answer 16

Primary:
* Result of first exposure to an antigen.
* Memory cells produced by clonal selection lend protection on subsequent encounters with pathogen.
* Slow and weak.

Seondary:
* result of second exposure to same antigen.
* Memory cells bind to antigens faster and produce larger amt of clones.
* Fast and stronger.

Question 17

Autoimmune disease

Answer 17

Immune system turns against the body’s own molecules.
* Multiple sclerosis: T cells attack myelin sheath of neurons; impairs signalling to various parts of the body, resulting in numbness, tremor, and vision loss.

Question 17

What are vaccines?
How do they work?

Answer 17

Vaccines are inactive form or part of a microbe (antigen) that stimulate the production of memory cells (primary response). If we come across the same pathogen again, plasma cells secrete more antibodies than in primary response which results in a faster activation of helper and cytotoxic T cells

Question 18

Immunodeficiency disease

Answer 18

Immune system components don’t function correctly, frequent infections.

HIV AIDS
* HIV may progress to AIDS if untreated
* Virus attacks helper T cells; cell-mediated and humoral immunity are impaired.
* Increases risk of opportunistic infections.

Severe combined immunodeficiency (SCID), a genetic disease that affects T and B lymphocytes.

Question 19

What is herd immunity?

Answer 19

The indirect protection of vulnerable individuals against a disease that happens when a significant portion of the population are immune (ie. thru vaccination).

Question 20

What are allergies

Answer 20

Abnormal overreactions to allergens (antigens) in surroundings

Question 21

How do allergies develop?

Answer 21

1. An allergen enters body.
2. B cells make antibodies
3. antibodies attach to mast cell.
4. allergen binds to antibodies on mast cell.
5. Histamine released, causing allergy symptoms.