Leucocytes and inflammation

Question 1

Two lineages of leucocytes

Answer 1

• Lymphoid (Lymphocytes) – small, bland-looking cells
• Myeloid – larger cells; most have prominent cytoplasmic granules and are called granulocytes

Question 2

Cells of the immune system and their function

Answer 2

Macrophage - phagocytosis and activation of bactericidal mechanism, Antigen presenting

Dendritic cell - Antigen presentation

Neutrophil - phagocytosis and bactericidal mechanisms

Eosinophils - Killing of parasites

Basophils - unknown

Mast cells - release of granules containing histamine

Question 3

Explain phagocytosis

Answer 3

Organism phagocytosed into a phagosome, which then fuses with a lysosome containing digestive enzymes. The organism is killed in this ‘phagolysosome’ by low pH, digestive enzymes, toxic free radicals and hydrogen-oxygen products

Question 4

What is released by phagocytes in local inflammation?

Answer 4

Cytokines

–Tumour necrosis factor alpha (TNF-alpha)

–Interleukin-1 (IL-1)

–Interleukin-6 (IL-6)

Chemokines: CXCL8

•Cytokines and chemokines promote local inflammation by:

–Attracting other cells, particularly neutrophils

–Acting on blood vessels to cause:

• Vasodilation
• Increased permeability
• Increased adhesion molecules on blood vessel endothelium

Question 5

What are the main features of systemic inflammation?

Answer 5

•Main features are:

–Fever, fatigue, muscle pain, anorexia

–With time, loss of muscle and fat

•Systemic inflammation is largely caused by cytokines

–Released into circulation

–Effect on distant tissues

Question 6

Effects of IL-1/IL-6/TNF-a on these organs:

• Liver
• Bone marrow endothelium
• Hypothalamus
• Fat, muscle

Answer 6

Question 7

What are the 4 outcomes of inflammation?

Answer 7

• Resolution: insult removed, tissue heals completely
• Fibrosis: insult removed, but tissue is scarred
• Chronic: insult cannot be removed
• Abscess formation

Question 8

Some observations: good things about inflammation

Answer 8

• Amplifies the immune response
• Small stimulus creates large local & systemic response
• Focuses the immune response
• Brings in cells required to contain infection and activate healing process when infection is cleared
• Activates the next stages of immunity (B cells/ T cells)
• This is the next line of defence, and also how the immune system learns (memory)

Question 9

Observations: bad things about inflammation

Answer 9

• May damage healthy tissue
• May be activated inappropriately (without infection)
• May be activated in an uncontrolled manner: septic shock