2024 - Chronic Inflammation - year 1

Definition: Specific form of chronic inflammation characterized by aggregation of macrophages.
- Epithelioid Macrophages: Enlarged macrophages with an epithelium-like appearance.
- Granuloma: Nodular collection of epithelioid macrophages surrounded by lymphocytes.
- Giant Cells: Large cells with multiple nuclei formed from the fusion of macrophages.

Seen in response to persistent irritants that are poorly digestible or initiate cell-mediated immune responses:
- Poorly Digestible Substances: Resist lysosomal breakdown.
- T-Cell Hypersensitivity: Induced by certain substances.
- Goal: Control or remove the damaging agent.

Occurs in response to poorly digestible foreign material:
- Exogenous: Splinters, sutures, graft materials.
- Endogenous: Keratin, hair shafts (e.g., in pilonidal sinus).

Involves interactions between CD4 T helper cells and macrophages:
- Macrophages present antigens via MHC II to CD4 helper T cells, activating them.
- Results in cytokine production (e.g., IL-2, IFN-γ).
Associated Conditions: TB, fungal infections, sarcoidosis.

Foreign Body Granuloma:
- Macrophages cluster around foreign material.
- Presence of multinucleated giant cells with disorganized nuclei.

Caused by Mycobacterium tuberculosis.
Induces type IV hypersensitivity; primarily affects lungs and lymph nodes.
Histological Features:
- Caseating granuloma, central necrosis.
- Presence of epithelioid macrophages, Langhans giant cells, T-helper cells, plasma cells, and peripheral suppressor T cells and fibroblasts.
Diagnostic Techniques: ZN stain, culture, fluorescent staining with auramine, PCR.

Granulomatous condition of unknown origin, more common in young adults, especially Blacks.
Histological Features:
- Non-caseating naked granuloma.
- Presence of Schaumann bodies (concentric calcifications) and asteroid bodies.

Acute Inflammation: Serous, fibrinous, suppurative, ulcers, sinus, fistula.
Serous Inflammation:
- Accumulation of thin fluid from serum or mesothelial lining.
- Examples: Skin blisters, effusions in peritoneal, pleural, and pericardial cavities.

Characterized by large amounts of pus.
- Often associated with organisms like Staphylococcus, which can lead to abscess formation.

Localized collection of pus that contains dead and degenerate leukocytes, host tissue cells, and microorganisms.

Local defects in epithelial surfaces caused by the shedding of dead epithelial cells, with significant tissue loss distinguishing them from erosions.
Types:
- Acute Ulcers: Full-thickness loss, may or may not scar.
- Chronic Ulcers: Deep, always associated with scarring.

Sinus: Tract lined by granulation tissue connecting a chronically inflamed cavity to a surface.
Fistula: An abnormal communication between two surfaces, e.g., gastrointestinal fistula in Crohn's disease.

Acute Phase Response: A systemic inflammatory syndrome generated by inflammatory mediators from leukocytes and hepatocytes in response to injury or infection.

Pyrexia: Triggered by bacterial pyrogens stimulating release of IL-1 and TNF-α, increasing cyclooxygenase and leading to prostaglandin production.
Acute phase proteins: Liver-produced proteins like C-reactive protein (CRP), serum amyloid A (SAA), and fibrinogen; associated with increased ESR.
Leucocytosis: Increase in white blood cell counts ranging from 4-8 to 15-20; extreme elevations may indicate leukemoid reactions or leukemia.
Clinical Features: Increased pulse and blood pressure, increased sweating, rigors, fatigue, malaise, and possible severe sepsis leading to DIC, hypotension, and shock.