S3) Chronic Inflammation Flashcards
What is chronic inflammation?
- Chronic inflammation refers to the prolonged inflammatory response that involves a progressive change in the type of cells present at the site of inflammation
- It is characterised by the simultaneous destruction and repair of the tissue from the inflammatory process
Why does chronic inflammation occur?
Chronic inflammation takes over acute inflammation in a few hours if the injurious agent is not quickly removed (hence, persists)
How does chronic inflammation present?
With regards to the four clinical signs of acute inflammation, redness and heat resolve but swelling but pain persists in chronic inflammation
What is the dominant cell in chronic inflammation?
The dominant cell in this type of inflammation is the macrophage and the process is more sophisticated than that seen in acute inflammation
What are the possible injurious agents causing chronic inflammation?
- Micro-organism
- Necrotic tissue
- Foreign body
- Crystalline substance
- Antigen
Draw a comparison between chronic and acute inflammation in terms of the following:
- Cells involved
- Chemical mediators involved
- Lesion formed
- Clinical examples
How can chronic inflammation arise?
- Takes over from acute inflammation (most common)
- Begins without preceding acute inflammation, e.g. tuberculosis, RA
- Develops alongside and superimposed on acute inflammation e.g on-going bacterial infection
Describe the microscopic appearance of chronic inflammation
- Macrophages and lymphocytes are present
- Granulation tissue begins to form
Identify the cells principally involved in chronic inflammation
- Macrophages
- T and B lymphocytes
- Eosinophils
- Fibroblasts
- Myofibroblasts
In the context of chronic inflammation, what are macrophages?
Macrophages are derivatives of blood monocytes and migrate into tissue spaces at the site of inflammation, after neutrophils, to take over from them
What are the functions of macrophages?
- Phagocytosis
- Antigen presentation
- Activate other cells (secrete substances)
- Stimulate angiogenesis
- Induce fibrosis
- Induce fever, acute phase reaction and cachexia
In the context of chronic inflammation, what are lymphocytes?
Lymphocytes are cells of the immune system which are present in tissues where there is antigenic material
What are the functions of lymphoctes?
- Process antigens
- Secrete antibodies (B lymphocytes)
- Secrete cytokines (T lymphocytes)
- Kill tumour / virus-infected cells (natural killer cells)
What are eosinophils and what do they do?
Eosinophils are immune cells which attack large parasites such as worms and they are present in high numbers in some immune responses e.g. in the bronchi in asthma, Hodgkin’s lymphoma
What do fibroblasts do?
- Respond to chemotactic stimuli and move to sites where they are needed
- Produce connective tissue substances e.g. collagen, elastin and GAGs
- Differentiate into myofibroblasts (can contract)
What are giant cells?
- Giant cells are cells formed when macrophages fuse with each other in circumstances when foreign bodies / certain bacterial infections are present
- These cells can be very large, contain dozens to hundreds of nuclei and are seen in granulomatous inflammation
What are the three types of giant cell?
- Touton giant cells
- Langhans giant cells
- Foreign body giant cells
Describe the structure of Langhans giant cells.
Where are they often seen?
- Nuclei are arranged around the periphery of the giant cell
- Often seen in tuberculosis (not exclusively)
Describe the structure of foreign body giant cells.
Where are they often seen?
- Nuclei are arranged randomly in the giant cell
- Often seen when an indigestible foreign body is present (not exclusively)
- Large foreign bodies stick to cell surface, small foreign bodies are phagocytosed