┌────────────────────────────────────────────┐
│     Environmental Challenge / Stress       │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  Keratinocyte Antigen Expression /         │
│  Production of Heat Shock Proteins (HSP)  │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  Unmasking of Self-Antigen                 │
│  (Self-peptide or HSP as antigenic         │
│   stimulus in autoimmune disease)          │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  Recognition of Self-Antigen by            │
│  T-Lymphocytes                             │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  Migration of T-Lymphocytes into           │
│  the Oral Epithelium                       │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  Activation of Auto-Cytotoxic CD8+ T-Cells │
└──────────────────┬─────────────────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  Keratinocyte Apoptosis via 3 Pathways:    │
├───────────────┬──────────────┬─────────────┤
│  TNF-α        │  Fas Pathway │ Granzyme B  │
│  Pathway      │              │ Pathway     │
│               │              │             │
│ T-cell        │ T-cell       │ Granzyme B- │
│ secretes      │ CD95L (FasL) │ mediated    │
│ TNF-α         │ binds to     │ cell death  │
│ → binds       │ CD95 (Fas)   │             │
│ TNF-α R1 on   │ on           │             │
│ keratinocyte  │ keratinocyte │             │
└───────────────┴──────────────┴─────────────┘
                   │
                   ▼
┌────────────────────────────────────────────┐
│  "Liquefaction Degeneration"               │
│  Apoptosis of Basal Epithelial Cells       │
│  → ORAL LICHEN PLANUS                      │
└────────────────────────────────────────────┘

1. Trigger - Environmental stress causes keratinocytes to express or unmask antigens (self-peptide or HSP).
2. Immune activation - T-lymphocytes recognize the self-antigen and migrate into the epithelium.
3. Effector cells - Auto-cytotoxic CD8+ T-cells are activated and attack basal keratinocytes.
4. Three apoptotic pathways:
   • TNF-α binds TNF-α R1 receptor on keratinocyte
   • FasL (CD95L) binds Fas (CD95) on keratinocyte
   • Granzyme B directly kills the cell
5. Outcome - Liquefaction degeneration and basal cell apoptosis → OLP lesions