2- Cells and Tissues in the Immune System

Question 1

What is a leukocyte?

Answer 1

Any white blood cell

Question 2

What is a lymphocyte?

Answer 2

A type of WBC (T cell, B cell, NK cell)

Question 3

What is a granulocyte?

Answer 3

Polymorphonuclear cells= neutrophils, eosinophils, basophils

Question 4

What are mononucleated cells?

Answer 4

lymphocyte or monocytes

Question 5

What is the percentage of basophils in circulation? What is their half-life?

Answer 5

0.5%
1-2 days
important in allergy and parasitic infections

Question 6

What is the percentage of eosinophils in circulation? What is their half-life?

Answer 6

1-3% of WBC in circulation
30 minutes
important in control of extracellular parasites

Question 7

What is the percentage of monocytes in circulation? What is their half-life?

Answer 7

3-7% in circulation
1-2 days
Once in tissues, mature into macrophages
Important role in phagocytosis and killing of bacteria, presentation of antigen on MHC II, and secretion of cytokines

Question 8

What is the percentage of neutrophils in circulation? What is their half-life?

Answer 8

55-90% of WBCs in circulation
1-2 days (usually 8-10 hours)

Question 9

What is the role of neutrophils in immune response to bacterial infections?

Answer 9

• first responders- arrive in substantial numbers within 4 hours
• exit the blood stream at the site of infection and accumulate in large numbers to ingest and kill pathogens
• bone marrow increases production of neutrophils in response to bacterial infections resulting in neutrophilia (elevated count in blood)
• main component of pus

Question 10

What is neutropenia?

Answer 10

Lower than normal numbers of neutrophils in the blood stream; can be seen in patients with viral infection

Question 11

What is the percentage of lymphocytes in circulation? What is their half-life?

Answer 11

20-30%
120 days
circulate looking for the one antigen they recognize, if do not come in contact with their antigen, they die

Question 12

Why are endothelial cells lining blood and lymph vessels important?

Answer 12

• regulate leukocytic traffic
• have adhesion molecules, called addressins, that allow circulating leukocyte to know where they are in the body

Question 13

All immune cells originate from bone marrow. What are the three lineages?

Answer 13

• erythroid: RBCs, platelets
• Myeloid: monocytes, neutrophils, eosinophils, basophils and some dendritic cells- important in the immune response, Mast cells
• lymphoid: B cells, T cells, NK cells, some dendritic cells

Question 14

Where do granulocytes mature?

Answer 14

they are released in a mature state

Question 15

Where do dendritic cells mature?

Answer 15

migrate to tissues and mature
important sentinel cells and antigen-presenting cells
key in the initiation of adaptive immunity

Question 16

Where do mast cells mature?

Answer 16

precursors leave bone marrow and mature in tissues

Question 17

Where do T lymphocytes mature?

Answer 17

Released immature from the bone marrow as pre-t cells, which go to the thymus to mature

Question 18

Where do B lymphocytes mature?

Answer 18

Released immature from the bone marrow as pre-B cells, which mature in primary lymphoid tissue
- birds: bursa of fabricus
- mammals: bone marrow

Question 19

Where do NK cells mature?

Answer 19

Released mature from the bone marrow, ready to function
- non-antigen specific
- no memory and part of innate immunity