General
On this page 4 sections
One Liners
- Epithelioid cells are specialized, modified macrophages = derived from circulating monocytes/mononuclear phagocytes
- Langhans' giant cells are multinucleated giant cells characteristic of granulomatous inflammation = derived from macrophages
- Pyogenic cocci (such as Staphylococcus aureus or Streptococcus pyogenes) trigger a prominent acute inflammatory response = rapid recruitment and activation of neutrophils
- Ulcer in burn tissue = Marjolin
- Ulcer in stomach = Curlings
- Lysosomal Storage disease = Tay Sach
- Antigen appear on RBC = 20th week
- TRALI reaction seen in = within 4 hours
- Yellow fever = councilmen bodies found
- Kartegenar's syndrome is a subgroup of primary ciliary dyskinesia (PCD) characterized by the classic triad = situs inversus, chronic sinusitis, and bronchiectasis/recurrent respiratory infections due to defects in ciliary dynein arms.
- Alpha = most ionising radiation
- Hydroxyproline : The clinical presentation (enlarged skull, enlarged vertebrae, and raised serum alkaline phosphatase) describes Paget's disease of bone = urinary hydroxyproline
Cells
| Cell | Main function | Most important when? | Key association |
|---|---|---|---|
| 🔵 Neutrophils | Phagocytosis; kill bacteria/fungi using enzymes, ROS | Acute bacterial infection, acute inflammation | First responders |
| 🟠 Eosinophils | Kill parasites; modulate allergic reactions | Parasitic infections, allergies/asthma | IL-5, IgE, parasites |
| 🟣 Basophils | Release histamine, heparin and other mediators | Immediate hypersensitivity/allergy | Similar to mast cells |
| 🟢 Mast cells | Histamine, leukotrienes, prostaglandins; immediate inflammatory response | Type I hypersensitivity, allergy, anaphylaxis | IgE + mast cell |
| 🟤 Macrophages | Phagocytosis; cytokine production; antigen presentation; tissue repair | Chronic inflammation, later stages of acute inflammation | Chronic inflammation |
| 🟡 Monocytes | Circulate in blood → become macrophages/dendritic cells in tissues | Chronic inflammation, tissue injury | Blood precursor of macrophages |
| 🟦 T lymphocytes | Cell-mediated immunity; regulate/kill infected cells | Viral infections, intracellular organisms, autoimmune disease | Type IV hypersensitivity |
| 🟥 B lymphocytes | Produce antibodies after differentiation into plasma cells | Extracellular bacteria, humoral immunity | → Plasma cells → antibodies |
| 🟪 Plasma cells | Produce large amounts of antibodies | Chronic infection, antibody-mediated immunity | Antibody factory |
| 🟩 NK cells | Kill virus-infected and tumor cells without prior sensitization | Viral infections, tumors | Innate cytotoxicity |
| ⚪ Dendritic cells | Capture/process antigen and activate naïve T cells | Initiation of adaptive immunity | Best APC for naïve T cells |
Lesions
| Condition | What is it? | Typical cause | Main cells | Hallmark | Acute / Chronic |
|---|---|---|---|---|---|
| Cellulitis | Diffuse inflammation of soft tissue without a localized pus cavity | Usually bacterial infection, especially Streptococci/Staphylococci | Neutrophils | Diffuse spreading inflammation, erythema, warmth, swelling | Acute |
| Abscess | Localized collection of pus within a tissue cavity | Pyogenic bacteria, especially Staph. aureus | Neutrophils + necrotic debris | Pus-filled cavity | Acute → may become chronic |
| Phlegmon | Diffuse suppurative inflammation spreading through tissue planes | Pyogenic bacterial infection | Neutrophils | Diffuse pus-producing inflammation without a well-defined cavity | Acute |
| Furuncle (boil) | Localized infection of a hair follicle | Usually S. aureus | Neutrophils | Pus around hair follicle | Acute |
| Carbuncle | Cluster of interconnected furuncles | Usually S. aureus | Neutrophils | Multiple interconnected abscesses with several drainage points | Acute |
| Granuloma | Organized collection of activated macrophages | Persistent infection, foreign material, immune disease | Epithelioid macrophages + giant cells + lymphocytes | Epithelioid cells ± giant cells | Chronic |
| Caseating granuloma | Granuloma with central caseous necrosis | Classically Mycobacterium tuberculosis | Epithelioid macrophages, Langhans giant cells, lymphocytes | Caseous necrotic center | Chronic |
| Foreign-body granuloma | Granulomatous reaction around foreign material | Sutures, splinters, talc, etc. | Macrophages + foreign-body giant cells | Foreign material surrounded by giant cells | Chronic |
| Serous inflammation | Accumulation of thin, watery fluid | Mild injury, burns, viral infection | Few inflammatory cells | Clear watery fluid | Acute |
| Fibrinous inflammation | Fibrin-rich exudate deposited on surfaces | Severe vascular injury | Neutrophils + fibrin | Fibrin deposition | Acute |
| Ulcer | Loss of surface epithelium with underlying tissue necrosis/inflammation | Trauma, infection, ischemia, malignancy | Depends on cause | Surface defect | Acute or chronic |
Hypersensitivity Reaction
| Type | Main mediator | Basic idea | Timing |
|---|---|---|---|
| Type I | IgE + mast cells | Immediate allergy | Minutes |
| Type II | IgG/IgM against cells/receptors | Antibody attacks a specific target | Hours |
| Type III | Immune complexes | Antigen-antibody complexes deposit in tissues | Hours–days |
| Type IV | T cells | Cell-mediated reaction | 48–72 h |
Calcifications
| Feature | Dystrophic | Metastatic |
|---|---|---|
| Tissue | Dead/damaged | Normal |
| Serum Ca²⁺ | Normal | Usually ↑ |
| Main problem | Tissue injury | Calcium/phosphate imbalance |
| Necrosis | Usually associated | Usually absent |
| Examples | Atherosclerosis, TB, damaged valves | Hyperparathyroidism, vitamin D excess |
| Common organs | Damaged tissues | Kidney, lungs, gastric mucosa |