Interferon-Gamma and the JAK-STAT Axis in Vitiligo
Autoreactive T cells release IFN-γ that overdrives JAK-STAT signaling in skin.
- IFN-γ: Key cytokine (driven by CD8+ T cells)
- JAK1/JAK2: Kinases involved (receptor-associated)
- STAT1: Downstream factor (drives CXCL9/10)
- Melanocyte loss: Result (depigmented patches)
Overactive signaling loop
Placeholder: short note on the IFN-γ/JAK/STAT feedback loop in vitiligo lesions.
Ruxolitinib Cream (Opzelura) Mechanism of Action
Ruxolitinib competitively blocks ATP binding at JAK1 and JAK2 kinase domains.
- JAK inhibitor: Drug class (topical formulation)
- JAK1, JAK2: Targets (selective inhibition)
- Opzelura: Brand name (FDA approved 2022)
- Twice daily: Application (affected areas)
Topical kinase inhibition
Placeholder: short note on ruxolitinib absorption and local kinase blockade.
Downstream Interferon Signal Quieting
With JAK blocked, STAT1 phosphorylation and IFN-γ target genes drop.
- Reduced: STAT1 activity (less phosphorylation)
- CXCL9/10 ↓: Chemokines (less T-cell recruitment)
- Weeks: Onset (gradual suppression)
- Lower: Inflammation (lesion quieting)
Breaking the feedback loop
Placeholder: short note on reduced chemokine signaling halting T-cell attack.
Follicular Melanocyte Stem Cell Reawakening
Hair follicle melanocyte reservoirs reactivate once inflammation subsides.
- Hair follicle bulge: Reservoir site (stem cell niche)
- Reduced IFN-γ: Trigger (permissive niche)
- Outward: Migration (toward epidermis)
- Months: Timeframe (gradual repopulation)
Stem cell migration
Placeholder: short note on melanocyte stem cells repopulating epidermis.
Best-Responding Site: Facial Repigmentation Outcomes
Face and neck respond best due to dense follicular melanocyte reservoirs.
- Face: Best site (high follicle density)
- ~50%: Response rate (≥75% facial repigmentation)
- 24–52 wk: Trial duration (TRuE-V studies)
- Hands/feet: Worst site (few follicles)
Site-dependent response
Placeholder: short note on why facial skin repigments faster than acral skin.
Placeholder: short highlight on facial response being the clinical benchmark.