Chronic inflammation is inflammation that lasts for a prolonged period of time, from weeks to years. It is characterized by ongoing inflammation, tissue damage, and healing. The dominant cells involved are macrophages, lymphocytes like CD4 T cells, and plasma cells. Chronic inflammation occurs when antigens or toxins cannot be eliminated, such as with persistent infections, autoimmune diseases, or prolonged exposure to toxic agents. It is mediated by cytokines that amplify and prolong the inflammatory response.

1. Chronic inflammation

2. SLOs
• Define
• Characteristics
• Types
• Cells involved
• Granulomatous reaction

3. Definition
• Inflammation of prolonged duration
(weeks to years) in which continuing
inflammation, tissue injury, and healing,
often by fibrosis, proceed simultaneously

4. Charaterictics
• Infiltration with mononuclear cells
• Tissue destruction
• Repair

5. Settings: Antigens cannot be
eliminated
• Persistent infections : Tuberculosis
(Delayed-type hypersensitivity)
• Immune-mediated inflammatory diseases :
autoimmune diseases & allergic diseases
• Prolonged exposure to potentially toxic
agents: Silica
• Alzheimer disease, atherosclerosis,
metabolic syndrome

6. Macrophages

7. Macrophages
• dominant cells
• circulating blood monocytes
• Mononuclear phagocyte system
• migrate within 24 to 48 hours

9. Role of macrophage
• ingest and eliminate microbes and dead
tissues
• initiate the process of tissue repair
• secrete mediators of inflammation
• display antigens to T lymphocytes and
respond to signals from T cells

10. Lymphocytes

11. Lymphocytes
• T Lymphocytes – CD4 , CD 8
• B Lymphocytes
• Plasma cells

12. Types of CD4 Lymphocytes
• TH1 cells : IFN-γ – activates macrophages
• TH2 cells : IL-4, IL-5, and IL-13 - recruit
and activate eosinophils and macrophages
• TH17 cells : IL-17 – recruit neutrophils and
monocytes

13. • TH1 and TH17 cells : bacteria, viruses and
autoimmune diseases
• TH2 cells: helminthic parasites and
allergic inflammation

15. Eosinophils
• parasitic infections
• Immune reactions mediated by IgE
• major basic protein
– toxic to parasites
– epithelial cell necrosis

16. Mast cells
• Connective tissue
• IgE armed
• allergic reactions including anaphylactic
shock

17. Granulomatous
• characterized by aggregates of activated
macrophages with scattered lymphocytes
• “walls off” the offending agent

20. Settings
• persistent T-cell responses
– Tuberculosis
• Immune mediated inflammatory diseases
– Crohn’s disease
• unknown etiology
– Sarcoidosis
• inert foreign bodies
– Suture

21. Summary
• Response to persistent stimulus
• Microbes that resist elimination, antigens and
• toxic substances
• Persistent inflammation, tissue injury, repair
• Activated macrophages, lymphocytes, and
plasma cells, often with prominent fibrosis
• Mediated by cytokines with a tendency to
amplify and prolong inflammatory response