Adaptive Defenses Study Guide

Question 1

two arms of adaptive immunity + what lymphocytes play a role in each

Answer 1

• humoral/antibody mediated immunity - b cells
• cellular/cell-mediated immunity - t cells

Question 2

humoral/antibody mediated immunity

Answer 2

• “Antibody Mediated”
• Immunity is provided by antibodies in the body’s fluids - blood and lymph
• Antibodies are produced by lymphocytes but circulate freely
• Antibodies bind to extracellular targets and mark them for destruction by phagocytes

Question 3

cellular/cell-mediated immunity

Answer 3

• Protection provided by lymphocytes
• The targets are cells infected by pathogens, cancer cells, or cells of foreign grafts
• Lymphocytes attack directly by killing the infected cells or indirectly by releasing chemicals
• Chemicals enhance the inflammatory response or activate macrophages

Question 4

What type of lymphocyte produces antibodies?

Answer 4

B lymphocytes of the humoral immunity

Question 5

How do antibodies fight invasion?

Answer 5

Antibodies bind to extracellular targets and mark them for destruction by phagocytes

Question 6

What kinds of cells are targeted in cell-mediated immunity?

Answer 6

Cells infected by pathogens, cancer cells, or cells of foreign grafts

Question 7

4 characteristics of adaptive immunity

Answer 7

• It involves *lymphocytes: B-Cells and T-Cells
• It is *specific: recognizes and targets identified pathogens/foreign substances
• is it *systemic: not restricted to the initial infection site
• It has *memory: after priming, it can mount stronger attacks

Question 8

Antigens

Answer 8

antibody generating – they are large, unfamiliar, complex molecules that are intruders or non-self. They are substances that can mobilize adaptive defenses. Complete antigens have immunogenicity – the ability to stimulate specific lymphocytes to proliferate, and reactivity – the ability to react with activated lymphocytes.

Question 9

Haptens

Answer 9

trouble some small molecules, incomplete antigens. Ex – chemicals found in poison ivy, animal dander, detergents, cosmetics, household products

Question 10

Is it possible for antigens to provoke immune responses in more than 1 type of leukocyte? how?

Answer 10

Many antigens have a variety of antigenic determinants (the specific parts of the antigen that are immunogenic) on their surface, so they have the ability to mobilize multiple leukocyte populations and produce multiple types of antibodies

Question 11

role of an APC

Answer 11

Antigen presenting cell – play auxiliary roles – they do not directly respond to antigens

Question 12

type of lymphocyte especially reliant on APCs

Answer 12

T cells (lymphocytes) cannot recognize antigens without apcs

Question 13

5 steps of lymphocyte development

Answer 13

1. Origin: Originate in red bone marrow - from what?
2. Maturation: Cells are “educated” to develop immunocompetence and self-tolerance
   Immunocompetence: ability recognize one specific antigen - once achieved, a unique antigen receptor is displayed on the lymphocyte’s surface
   Maturation of B-Cells occurs in Bone Marrow
   Maturation of T-Cells occurs in the Thymus
3. Seeding Secondary Lymphoid Organs: naive but immunocompetent B-Cells and T-Cells migrate to 2ndary lymphoid organs and await encounters with antigen
4. Antigen Encounter and Activation: antigen binds to the lymphocyte that has its receptor; that lymphocyte is selected for further development - clonal selection
5. Proliferation and Differentiation: once activated, the lymphocyte rapidly proliferates to form an army of cells (“a clone”) just like itself - with the same antigen specificity
   Most members of the clone become effectors (infection-fighting) cells, but some will become memory cells
   Memory cells will lie in wait for a subsequent encounter with the same antigen

Question 14

positive selection test in lymphocytes

Answer 14

the maturing lymphocyte must be able to recognize the MHC (inability to do this = apoptosis)

Question 15

negative selection tests for lymphocytes

Answer 15

the maturing lymphocyte must not recognize self-antigen (recognizing self antigen = apoptosis)

Question 16

What determines the diversity of our antigen receptors?

Answer 16

Our genes – not the antigens we encounter – determine which specific foreign substances our immune system will be able to recognize and resist; the diversity of receptors on our lymphocytes represents genetically acquired knowledge of the microbes likely to be in our environment

Question 17

The effector B-Cell is called a __________.

Answer 17

plasma cell

Question 18

plasma cells

Answer 18

They secrete antibodies that circulate in blood or lymph where they bind to free antigen and mark them for destruction

Question 19

What becomes of the non-effector B-Cells?

Answer 19

become memory cells – memory cells can mount an almost immediate humoral response when the same antigen is encountered in the future

Question 20

What are the effector T-Cells?

Answer 20

Cytotoxic t (tc) cells
Helper t (th) cells
Regulatory t (treg) cells

Question 21

Primary Immune Response

Answer 21

occurs on 1st exposure to antigen
- 3-6 day lag time
- B-cells specific to that antigen proliferate, offspring differentiates into antibody-secreting plasma cells
- Plasma antibody levels peak in about 10 days then decline

Question 22

Secondary Immune Response

Answer 22

occurs on any subsequent exposure to the same antigen
- Response is faster, more prolonged, and more effective; “priming” has already occurred
- 2-3 day lag time
- Plasma antibody concentrations rise sharply to much higher levels than the primary response
- Plasma antibody concentrations remain high for weeks to months
- Memory cells persist for long periods - can retain capacity to produce powerful humoral responses for life

Question 23

Active Humoral Immunity

Answer 23

your B-cells encounter antigens and produce antibodies against them
- can be natural or artificial

Question 24

natural active immunity

Answer 24

you contract a bacterial or viral infection, experience symptoms, and develop antibodies

Question 25

artificial active immunity

Answer 25

you receive a vaccine to prime your immune system

Question 26

Passive Humoral Immunity

Answer 26

ready-made antibodies are introduced - B-cells are not challenged, immunological memory does not occur
- can be natural or artificial

Question 27

Natural Passive Immunity

Answer 27

conferred on a fetus or infant when maternal antibodies cross the placenta or are ingested in breast milk

Question 28

Artificial Passive Immunity

Answer 28

administration of a donor’s antibodies - can be used to treat Hepatitis A, poisonous snake bites, rabies, and tetanus

Question 29

What type of immunity is garnered through a vaccine?

Answer 29

Artificial active immunity

Question 30

What role do booster shots play?

Answer 30

intensify the immune response

Question 31

What portion of an antibody is responsible for forming antigen-antibody complexes?

Answer 31

Variable regions – antibodies responding to different antigens have different variable regions

Question 32

defense mechanisms of antibodies

Answer 32

Neutralization
Agglutination
Precipitation
Complement Activation (Lysis)

Question 33

Neutralization

Answer 33

antibodies block specific sites on pathogens to prevent attachment to tissue cells - phagocytes destroy antigen-antibody complexes

Question 34

Agglutination

Answer 34

antigen-antibody complexes are cross-linked into large latices

Question 35

Precipitation

Answer 35

soluble molecules are cross-linked into large lattices that fall out of solution - once settled, soluble molecules are eaten by phagocytes

Question 36

Complement Activation (Lysis)

Answer 36

several antibodies bind close together on a cellular antigen and complement is activated - membrane attack complexes insert into the antigenic cell’s surface and cell lysis occurs

Question 37

Why are MHC proteins important?

Answer 37

• Major histocompatibility complex – proteins that help identify a cell as “self”
• Contain a self or foreign antigen
• Only identical twins have the same mhc
• T cells can only recognize antigens that are presented on mhc proteins
• Our self antigens are not antigenic to us, but highly antigenic to others

Question 38

difference in CD4 and CD8 cells

Answer 38

Cd4 can only bind with mhc II and cd8 can only bind with mhc I