Response to Injury III: Chronic Inflammation

Created by

Nazia Zannat

Cards (22)

How does chronic inflammation arise?
It arises as:
a progression from acute inflammation
following repeated episodes of acute inflammation
de novoif the causative agent only produces a mild acute response
What happens in chronic inflammation?
The process of tissue destruction takes place alongside that of healing and repair so it's integrated and the 2 processes should be considered together
What are the features of chronic inflammation?
It's very variable but some prevailing themes are:

- Tissue destruction & ulceration

- The inflammatory infiltrate is a mixture of macrophages, plasma cells, and lymphocytes; some polymorphs may be present

- The relative contribution of each cell type varies depending on the inflammatory stimulus

- Chronic inflammation is associated with the production of new fibrous tissue through granulation tissue formation (healing)
What is a mechanism of chronic inflammation?
Proliferation of macrophages and lymphocytes
What are the causes of chronic inflammation?
These signals converge on target cells, lymphocytes, macrophages, plasma cells, this will cause an inflammatory response
What pharmacological agents can you use to interfere with production of inflammatory mediators?
Aspirin
NSAIDs
Hydrocortisone
Antihistamines
Inhalers (various)
Other steroids
What patterns can you divide chronic inflammation into?
Serous
Fibrinous
Suppurative (purulent)
Granulomatous
What is granulomatous inflammation?
A form of chronic inflammation characterised by the formation of granulomas
What is a granuloma?
A collection of activated macrophages
What do granulomas look like histologically?
Abundant eosinophilic cytoplasm and look vaguely like epithelial cells so are termed 'epithelioid cells
What can macrophages aggregate to form?
Giant cells
What may solitary granulomas form in response to?
Persistent local inflammatory stimuli (e.g. foreign bodies)
What are some examples of chronic granulomatous diseases?
TB
Leprosy
Sarcoidosis
Crohn's disease
Oro-facial granulomatosis
Chronic granulomatosis disease
What is acid fast bacilli (AFB)?
A general term used to describe bacteria stained using the 'Ziehl Neelsen' (ZN) technique

In common usage, the term refers to M. tuberculosis
What happens in TB?
Mycobacteria are ingested into the macrophages which excite a T cell response

As they are intracellular, they are protected from immunological attack & persist in the tissues.
What is a caseating granuloma?
It is a cheese-like necrosis ( tissue death), typically a feature of a granuloma of TB

Features include:

-dense mass of epithelioid cells
-T lymphocytes
-caseous necrosis centrally,
-Langerhans type giant cells,
- AFBs
Why can TB be considered a (Type IV) hypersensitivity reaction? 
Because the intracellular mycobacteria drive ongoing inflammatory activity

This is characterised by a cell mediated (T cell) response

A sequel to this is tissue damage & repair

Tissue damage is caused by the hosts own cells
What is rheumatoid arthritis?
A chronic, systemic inflammatory disorder that mainly affects joints

These become deformed and painful with loss of function
It may also have extra-articular features
What makes rheumatoid arthritis a poly-arthritis?
Typically when >5 joints are involved
What cytokines are involved in the signalling pathway for inflammatory arthritis?
TNF-a
Interleukin-1
Interleukin-6
Describe the process of what happens in rheumatoid arthritis.
The inflammatory process causes the damage
Summarise chronic inflammation:
- Can be both protective and destructive

-Reflects a complex interrelationship between the response to damaging stimuli and hypersensitivity

-Is associated with granulation tissue formation and fibrous repair - in some instances this is helpful but in others it leads to tissue damage and loss of function.