Body's Defenses

Question 1

Define: immune response

Answer 1

The immune system’s response to a threat

Question 2

List and briefly describe 3 important aspects of the adaptive body defense. (3)

Answer 2

1. Antigen- specific → recognizes and acts against particular pathogens or foreign substances
2. Systemic → immunity is not restricted to the initiated infection site
3. “Memory” → it recognizes and mounts even stronger attacks on previously encountered pathogens

Question 3

Define: antigen

Answer 3

Any substance capable of mobilizing out immune system and provoking an immune response

Question 4

What are the 2 crucial cells of the adaptive defense? (2)

Answer 4

1. Lymphocytes

2. Antigen-presenting cells (APCs)

Question 5

Name and briefly describe the 2 major categories of lymphocytes. (2)

Answer 5

1. B lymphocytes (B cells) → produce antibodies and oversee humoral immunity
2. T lymphocytes (T cells) → are non-antibody producing lymphocytes

Question 6

State the 3 stages in the lymphocyte process. (3)

Answer 6

1. Undergo maturing process (2-3 days) directed by the thymic hormones (thymosin)
2. When lymph nodes bind with recognized antigens, they complete their differentiation into fully mature T and B cells
3. Antigen-activated (mature lymphocytes) effector and memory cells circulate continuously in the blood stream and lymphoid organs of the body

Question 7

Where do lymphocytes originate from?

Answer 7

Hemocytoblasts in the red marrow

Question 8

What happens to lymphocytes which bind to self-antigens?

Answer 8

They are vigorously weeded out and destroyed

Question 9

Are immature lymphocytes released from the marrow identical?

Answer 9

Yes

Question 10

How do immature lymphocytes differentiate into B or T cells? (2)

Answer 10

1. T cells arise from the lymphocytes that migrate to the thymus
2. B cells develop immunocompetence in bone marrow

Question 11

How many antigens can a single, immunocompetent lymphocyte react to?

Answer 11

Only the one, distinct antigen

Question 12

Where do T and B cells migrate to after gaining immunocompetence?

Answer 12

Both T and B cells migrate to the lymph nodes and spleen (loose connective tissue) where encounters with antigens occur

Question 13

What is the effect of the chemicals activated T cells release?

Answer 13

Activated T cells release chemicals that prod macrophages into becoming activated macrophages → they secrete bacterial chemicals

Question 14

Where do macrophages and T cells go in the body?

Answer 14

1. Macrophages remain fixed in lymphoid organs

2. T cells circulate

Question 15

What is the major role of antigen-presenting cells in immunity?

Answer 15

1. Engulf antigens

2. Present fragments of antigens like signals flags so that they can be recognized by T cells

Question 16

What do dendritic cells act as?

Answer 16

Mobile sentinels

Question 17

What do macrophages act as in the defensive system?

Answer 17

Phagocytes

Question 18

When are B lymphocytes stimulated to complete their development?

Answer 18

When antigens bind to their surface receptors → lymphocyte becomes primed

Question 19

What do lymphocytes undergo after the binding event?

Answer 19

Clonal selections

Question 20

What do the B cell clones become? (2)

Answer 20

1. Most become plasma cells

2. The rest become memory cells (which can respond at a later time)

Question 21

What are later immune responses called?

Answer 21

Secondary humoral responses

Question 22

What is active immunity?

Answer 22

When B cells encounter antigens and produce antibodies