Chronic inflammation
Contents
• Chronic inflammation
• Granulomatous inflammation
Objectives
At the end of this PDF, student will be able to
• Define ‘chronic inflammation’
• Explain the causes of chronic inflammation
• Describe the general features of chronic
inflammation
• Describe the pathogenesis granulomatous
inflammation
Chronic inflammation
Chronic inflammation is defined as
prolonged process in which tissue destruction and inflammation occur at the
same time
Chronic inflammation – Causes
1. Chronic inflammation following acute inflammation:
• Prolonged acute inflammation
• Tissue destruction is extensive
• The bacteria survive & persist in small numbers at the site of
acute inflammation
e.g. Osteomyelitis, pneumonia terminating
in lung abscess
2. Recurrent attacks of acute
inflammation:
• Repeated attacks of acute inflammation
• Culminate in chronicity of the process
e.g. – Recurrent urinary tract infection
leading to chronic pyelonephritis
– Repeated acute infection of gallbladder leading to chronic
cholecystitis
3. Chronic inflammation starting de
novo:
• Infection with organisms of low pathogenicity is chronic
e.g. infection with Mycobacterium tuberculosis.
General features of chronic inflammation
Mononuclear cell
infiltration
Infiltration of
chronic inflammatory lesions
• Phagocytes – circulating monocytes, tissue macrophages, epithelioid
cells, multinucleated giant cells
• Lymphoid cells
• Chemotactic factors and adhesion molecules for continued infiltration of macrophages
• Local proliferation of macrophages
• Longer survival of macrophages at the site of inflammation
Tissue
destruction or necrosis
• Brought about by activated macrophages
• Release a variety of biologically active substances
E.g. protease, elastase, collagenase, lipase, reactive oxygen radicals,
cytokines (IL-1, IL-8, TNF-α), nitric oxide,
angiogenesis growth factor
Proliferative changes
• Result of necrosis
• Proliferation of small blood vessels and fibroblasts is
• Formation of inflammatory granulation tissue
• Healing by fibrosis and collagen laying
Systemic effects of chronic inflammation
• Fever: mild fever, often with
loss of weight and weakness
• Anaemia
• Leucocytosis
• ESR: elevated in all cases
• Amyloidosis: Long-term cases of chronic suppurative Inflammation –
secondary systemic (AA) amyloidosis
Types of chronic inflammation
Non-specific
• Irritant substance – nonspecific chronic inflammatory
• Formation of granulation tissue
• Healing by fibrosis (chronic osteomyelitis, chronic ulcer)
Specific
Injurious agent causes a characteristic
histologic tissue response
e.g. tuberculosis, leprosy, syphilis
Granulomatous inflammation
Granuloma
• A tiny lesion about 1 mm in diamter
• Comprises of epitheloid cells in the centre
& lymphoid in the periphery
• Contains gaint cells
• Associated with necrosis & fibrosis
• Proliferation of fibroblast in the periphery
• Due to presence of micro organism
e.g. Mycobacterium
tuberculosis
– Poorly digestible
– Cell mediated immune response
Pathogenesis of granulomatous inflammation
• Type IV hypersensitivity reaction
• Engulfment by macrophages
• Presentation of microbes to CD4+ T cells
• Activation of T-cells
• Cytokines
Composition of Granuloma
• Epithelioid cells
• Multinucleate giant cells
• Lymphoid cells
• Necrosis
• Fibrosis
Summary
• Chronic inflammation is defined as prolonged process in which tissue
destruction and inflammation occur at the same time
• Chronic inflammation may occur due to prolonged
and recurrent attack of acute inflammation or may start de novo
• Chronic inflammation is characterized by mononuclear cell infiltration,
proliferation and necrosis
• Granulomatous inflammation occur by
proliferation of fibroblast in the periphery due to presence of micro organism
