Chronic Inflammation

Question 1

What is chronic inflammation?

Answer 1

Chronic response to injury with associated fibrosis

Question 2

Why does chronic inflammation arise?

Answer 2

1. Takes over from acute inflammation
2. Begins without any preceding acute inflammation e.g. TB and autoimmune conditions such as rheumatoid arthritis
3. When it develops alongside acute infection e.g. in on-going bacterial infection

Question 3

What does chronic inflammation look like?

Answer 3

Mononuclear cells (macrophages and lymphocytes) are the predominant cell type rather than neutrophils. A new type of tissue called granulation tissue begins to form as healing gets underway.

Question 4

What is a macrophage?

Answer 4

Type of white blood cell. They are large, specialized cells that recognize, engulf and destroy target cells. in circulating blood they are called monocytes and are only called macrophages once they enter the tissue space. They are produced in the bone marrow.

Question 5

What are the functions of macrophages?

Answer 5

• Phagocytosis
• Secretion of substances that summon/ activate other cells
• Present antigens to immune system
• Stimulate angiogenesis
• Induce fibrosis
• Induce fever, acute phase reaction and weakness/body wasting

Question 6

What are the functions of lymphocytes?

Answer 6

Process antigens, secrete antibodies, secrete cytokines and kill cells.

Question 7

What is the function of eosinophils?

Answer 7

They attack large parasites such as worms and are present in large numbers in some immune responses e.g. in the bronchi in asthma and in some tumours e.g. Hodgkin’s lymphoma

Question 8

What are the functions of fibroblasts?

Answer 8

Respons to chemotactic stimuli and move to sites where they are needed. Fibroblasts produce CT substances e.g. collagen, elastin and glycosaminoglycans.

Question 9

What are giant cells?

Answer 9

A fusion of macrophages into a single cell

Question 10

What are the three types of giant cell?

Answer 10

Langhans, foreign body and Touton.

Question 11

What are langhans giant cells?

Answer 11

Nuclei are arranged around the periphery of the giant cell, they are often (but not exclusively) seen in TB

Question 12

What are foreign body giant cells?

Answer 12

Nuclei are arranged randomly. They are often seen when a hard to digest foreign body is present. If the foreign body is small it is digested by the giant cell, if it is large the cell sticks to its surface.

Question 13

What are Touton giant cells?

Answer 13

Nuclei are arranged in a ring towards the centre of the cell. They form lesions where there is a high lipid content such as fat necrosis and xanthomas. Such lesions will also contain foam cells.

Question 14

What are foam cells?

Answer 14

Macrophages whose cytoplasm appears foamy as they have phagocytosed a lot of lipid

Question 15

Describe the unwanted effects of chronic inflammation

Answer 15

• Fibrosis and impaired function
• Involvement in inappropriate immune responses
• Tissue destruction
• Atrophy

Question 16

When does fibrosis occur?

Answer 16

Excessive scar tissue occurs when fibroblasts are stimulated by cytokines to produce excess collagen and is typically seen during chronic inflammation as it helps to wall off infected areas and the production of a fibrous scar to replace damaged tissue is essential in wound healing.

Question 17

How does chronic inflammation lead to impaired function?

Answer 17

Excessive or inappropriate fibrosis replaces normal parenchymal tissue and impairs the function of an organ e.g. interstitial fibrosis of the lung. If the area of fibrosis contains enough myofibroblasts it can slowly contract and cause further problems e.g. contraction in a cirrhotic liver will impair the flow of portal blood resulting in ascites.

Question 18

How is chronic inflammation involved in inappropriate immune responses?

Answer 18

Immune system attacks innocuous targets such as pollen (resulting in hay fever) or inappropriate targets such as the body’s normal tissues, as seen in autoimmune diseases such as rheumatoid arthritis.

Question 19

What is a granuloma?

Answer 19

A small area of inflammation around particles that are poorly soluble or difficult to eliminate e.g. thorns and splinters, tough bacteria (TB etc).

Question 20

What are epithelioid cells?

Answer 20

Macrophages that have become modified to look like epithelial cells in that they are elongated, have eosinophilic cytoplasm and appear tightly packed together.

Question 21

What are the two types of granulomas?

Answer 21

Foreign body granulomas

Hypersensitivity or immune type granulomas

Question 22

Describe foreign body granulomas

Answer 22

• Contain macrophages, foreign body giant cells, epitheliod cells and some fibroblasts (at the periphery)
• Very few/ no lymphocytes
• Develop around material that is not antigenic e.g. surgical thread

Question 23

Describe hypersensitivity granulomas

Answer 23

• Contain macrophages, giant cells (may be Langhans), epithelioid cells (more prominent than in foreign body type), some fibroblasts (at periphery) and lymphocytes
• Can undergo central necrosis esp in TB
• Develop around insoluble but antigenic particles
• Seen in sarcoidosis, Wegener’s and Crohn’s
• Can be harmful as they occupy parenchymal space within an organ

Question 24

What is sarcoidosis?

Answer 24

Disease of unknown cause in which granulomas are seen in organs throughout the body

Question 25

When does chronic inflammation typically arise?

Answer 25

• After or alongside acute inflammation
• Chronic persistant infections
• Autoimmune conditions
• Prolonged exposure to toxic agents