Macrophages and Granulocytes/Phagocytes and Phagocytosis

Question 1

What cells are phagocytes?

Answer 1

macrophages and neutrophils

Question 2

Do phagocytes need training?

Answer 2

no

Question 3

Are phagocytes part of the innate or adaptive immune system? Why?

Answer 3

Innate; rapid defense mechanisms, already present prior to exposure of foreign substances

Question 4

Compare and contrast PMN with mononuclear phagocytes: where do they reside?

Answer 4

PMN- release from bone marrow, last in blood for ~12 hours; bone marrow to blood
mononuclear phagocytes- in blood as monocytes/tissues as macrophages

Question 5

Compare and contrast PMN with mononuclear phagocytes: how long do they last?

Answer 5

PMN-

mononuclear phagocytes-

Question 6

Compare and contrast PMN with mononuclear phagocytes: can they survive in tissues for long periods?

Answer 6

PMN-

mononuclear phagocytes-

Question 7

What are some examples of specialized “tissue macrophages”?

Answer 7

lung- alveolar macrophages/intravascular macrophages
cutaneous- histiocytes/langerhans cells
Liver- Kupffer cells
Spleen/lymph nodes- reticuloendothelial system

Question 8

What signals the phagocytes to leave the blood stream?

Answer 8

Selectin/Integrin bind to phagocyte and bring them to site of inflammation
Rolling->adherence->emigration

Question 9

How are antigens recognized for phagocytosis?

Answer 9

PRRs, complement receptors, antibody receptors, cell adhesion molecules

Question 10

How are phagocytes “activated”?

Answer 10

gradually induced to heightened states of cellular activity by exposure to external stimulants:
chemotaxins
diapedesis
phagocytosis
cytokines (IFN-gamma/TNF-alpha)

Question 11

What are the results of activation?

Answer 11

increased efficacy of antimicrobial activities
acquisition of new capabilities such as ability to bind to, and kill tumor cells
increased efficiency of APC
secretion of proteins that influence inflammation and immunity
secretion of proteins that influence wound healing

Question 12

What 2 major pathways do phagocytes use to “kill” organisms?

Answer 12

killing through production of oxidizing radicals (respiratory burst)
lytic enzymes (phagolysosome within cell)

Question 13

What specific types of organisms do different phagocytes protect against?

Answer 13

Eosinophils/basophils/mast cells: agents too large for phagocytosis (intestinal parasites, HW)
Neutrophils: microbes (bacteria, fungal spores, protozoa) and disposal of other foreign material
Mononuclear phagocytes (MP) (monocytes and macrophages): microbes and large parasites