Chronic inflammation Flashcards
define Chronic inflammation
- inflammation of prolonged duration
- active inflammation ,tissue destruction and attempt at repair occurs simultaneously
- it is insidious (slow)
- often asymptomatic
- results in severe tissue damage and disabling human disease
what causes chronic inflammation 6
- Prolonged / persistent exposure to initial stimuli
- foreign material
- delayed healing
- lowered host resistance
- repeated acute inflammation
List the 2 types of chronic inflammation
- non specific
2. granulomatous
discuss the 3 morphological features of chronic inflammation
- Exudation
* Persistence of acute inflammatory changes with neutrophils ,fibrin ,fluid exudate and pus formation due to prolonged exposure of injurious agent
*results in continued tissue distruction
- Macrophages accumulation and proliferation
* demolition phase - Repair
* Angiogenesis: formation of new blood vessels
* proliferation of fibroblast which lay down collagen
* infiltration by other mononuclear cells eg plasma cells and leukocytes
Discuss the mononuclear infiltration, which is a central process
*Macrophage play a dominant role
Consist of the cells from the bone marrow ,blood monocytes and tissue macrophages
-Tissue macrophages are scattered in the connective tissue or in organs
eg liver = Kupffer cells
How are macrophages activated
There are 2 major pathways of macrophage activation
- Classical
- Alternative
The stimuli that activates ,macrophages by these pathways are and the function of activated cells are different
Discuss the classical pathway that activate macrophages
- Classical macrophage activation is :
- induced by microbial products eg endotoxin which engage TLF and other sensors
- T cell derieved signals and cytokine Interferon gamma gamma in immune responses
- foreign matter eg particular matter
- Classically activated macrophages are called M! produces nitric oxide and Reactive Oxygen Species and upregulate lysosomal enzymes which ,all which enhance the ability to phagocytose enzymes and secrete cytokines that enhance inflammation
- The M1 are capable of injuring normal tissues
Discuss the alternative activation of macrophages
- Induced by cytokines other than Interferon gamma such as IL4 and IL13 produced by lymphocytes and other cells
- These macrophages are called M2 macrophages which function by repairing tissue
- they secrete growth factors that stimulate angiogenesis ,active fibroblast and collagen synthesis
- They are not bactericidal
- cytokines produced may inhibit the classical activation pathway
What is the function of activated macrophages 4
- They ingest and eliminate microbes and dead tissue
- initiate the process of tissue repair and are involved in scar formation and fibrosis
- They secrete mediators of inflammation eg tumor necrosis factor ,il1 and chemokines thus they are central to initiation and propagation of inflammatory reaction
- Macrophages present antigens to T cells and respond to signals from T cells
What are the other cells involved in chronic inflammation
Lymphocytes
*Microbes and foreign antigens activate B and T cells
*Since they are mediators of the adaptive immune system , when they are present , the inflammation tends to be severe and persistent
*T helper cells produce cytokines that promote inflammation and the nature of the inflammation
*Activated b cells and plasma cells are present during chronic inflammation . Antibodies produced maybe against persistent foreign
or self antigens at the inflammatory site or altered tissue
Discuss the macrophage - lymphocyte interaction during chronic inflammation
*lymphocytes
*Macrophages present antigens to Tcells and produce cytokines (IL12) that simulate T cell responses
*Activated T cells secrete cytokines that recruit and activate other macrophages to promotes more antigen presenting and cytokine secretion
this is a bidirectional way and it results in cellular reaction that feu and sustain chronic inflammation
Besides lymphocytes and macrophages , which other cells are involved
Eosinophiles
- Are abundant in immune reactions mediated by IgE and in parasitic reactions
- Have granules that contain basic proteins and cationic proteins that is toxic to parasites and causes lyses pf epithelial cells
Mast cells
* Has receptors that bind to Fc site on IgB antibodies
*During immediate hypersnsitivity ,IgE bound to cells receptors recognize antigens and the cells degranulate and release
mediators such as histamine
*This reaction occurs during allergic reaction
*
Give example of non specific chronic inflammation
- Chronic osteomyelitis
- Chronic bronchitis
- chronic pyelonephritis
- chronic cholecystitis
Discuss chronic osteomyelitis
- occurs in long bones of children and young adults
- Follows acute inflammation in bone
- Due to exudate against bone and compression against blood vessels result in ischemia and necrosis
- Pus is formed which is discharged through the skin via sinuses
- The dead bone acts as a foreign body and organisks continue t grow = sequestrum
- The dead bone maybe broken down by osteoclasts but not completely removed thus there are other attempts at healing and formation of ne bone
- new bone id formed by periosteum which encases the sequestrum known as involucrum
- End result is chronic inflammation of bone or chronic osteomyelitis
Discuss the chronic bronchitis
- Chronic cough with production of sputum for 3 months in at least 2 consecutive years
- Cause ; cigarette irritating the airways and damages the epithelial cells and predispose to infection
- Histology : increase in number and size of mucous producing glands in bronchial wall with increased number of goblet cells in the epithelium
- Hyperaemia and oedema of the submucosa with lymphocytic infiltration later resulting in scaring of bronchial wall