T3: Chronic Inflammation Flashcards
What are the causes of chronic inflammation?
- Progression from acute e.g. helicobacter pylori.
Recurrent episodes of acute e.g. chronic cholecystitis. - Persistent infection by certain microorganisms (difficult to remove).e.g. TB, leprosy.
- Prolonged exposure to potentially toxic agents (endogenous e.g. bone, exogenous e.g. asbestos fibres, sutures).
- Autoimmunity e.g. Hashimoto’s thyroiditis.
- Unknown e.g. Crohn’s disease, ulcerative colitis, sarcoidosis.
What cells are involved in chronic inflammation?
- Macrophages
- Lymphocytes
- Other Mononuclear cell such as eosinophils and mast cells.
- Fibroblasts
- Plasma cells
What is the difference between granulomatous inflammation and granulation tissue?
Granulation tissue is the development of new blood vessels and fibrous scarring during chronic inflammation.
Granulomatous inflammation: Inflammation in which there is granuloma.
What are Langhan’s giant cells?
Langhans-type giant cells. Giant cells are collections of macrophages that have fused together to form one giant cell as they are struggling to break down the causative agent. In a Langhans-type giant cells - the nuclei are structured around the perimeter of the cell in the shape of a horse shoe. This is seen in tuberculosis for example.
What are foreign body giant cells?
Giant cells are collections of macrophages that have fused together to form one giant cell as they are struggling to break down the causative agent. A multinucleate giant cell (foreign body giant cell), the nuclei are scattered. These are seen characteristically in relation to particular foreign body material.
What are are epithelia histiocytes?
Epithelia histocytes are named for their vague resemblance to epithelial cells. They are have large vesicular uncle, plentiful eosinophilic cytoplasm and are often elongated. They tend to be elongated. They have little phagocytic activity but are adapted for a secretory function. They then form granulomas.
What is a granuloma?
Granuloma = collection of activated epithelioid macrophages (pink cytoplasm, indistinct cell membranes, oval nucleus).It may also include lymphocytes and histolytic giant cells.
Granulomatous diseases comprise of some of the most widespread and serious diseases such as tuberculosis and leprosy.
What is pathway to chronic inflammation?
- Tissue injury means that cells circulating in the blood are attracted by chemical mediators
- They adhere to the endothelium and emigrate through into surrounding tissues
- The macrophages phagocytises in the tissue and present that material to the T cells. Macrophages also produce various cytokines. The is activate T lymphocytes. Which activate B cells. B cells in turn become plasma cells and produce immunoglobulins. These activate T lymphocytes. These produce mediators that lead to chronic inflammation and activate microphages e.g. Interferon gamma activates more macrophages.
The mediators activate fibroblasts which lay down collagen in fibrosis. Some of the mediators also cause tissue injury. All of this usually occurs on a background of granulation tissue.
What is the difference between caseating and non-caseating granuloma?
Caseating granuloma - have caseating necrotic core in the centre (as seen in tuberculosis). Around this is, macrophages, Langhans’s type giant cells, lymphocytes, plasma seeks and fibroblasts.
A non-caseating epithelioid granuloma is the same without the necrosis.
Give examples of causes of granulomatous inflammation.
Granulomatous inflammation is caused by a very limited number of factors:
They are often things the macrophages struggle to phagocytose. They therefore activate further macrophages. The cycle continues and so we get a collection of activated macrophages.
- Bacterial (TB, leprosy, syphilis, cat-scratch)
- Parasitic (schistosomiasis)
- Fungal (histoplasma, cryptococcus)
- Inorganic metals or dust (silicosis, berylliosis)
- Foreign body (suture, vascular graft)
Diseases of unknown cause associated with granuloma (sarcoidosis, ulcerative colitis)
What are macroscopic appearances of chronic inflammation?
The most common appearances include:
- Chronic ulcer
- Chronic abscess cavity
- Thickening of the wall of a hollow viscus
- Granulomatous inflammation
- Fibrosis
We may see cachexia (tissue wasting) and anaemia of chronic disease.
What are microscopic features of chronic inflammation?
- Paracrine stimulation of connective tissue - angiogenesis followed by fibroblast production and collagen synthesis resulting in granulation tissue. This is regulated by growth factors.
- B lymphocyte and T lymphocyte infiltrate
- May present as amyloidosis
- Macrophage infiltration
What is chronic inflammation?
In chronic inflammation, you see cells of the innate and adaptive immune system. The onset is very slow and duration is long. In chronic inflammation we see angiogenesis (new blood vessel formation) and fibrosis (deposition to collagen by fibroblasts - cells that make collagen).
