Idopathic Inflammatory Myopathy

Question 1

Immunologic capabilities of muscle fibers

Answer 1

• expression of MHC -1 and MHC-II
• cytokine production
• lipids needed for T_cell interaction
• FAs ligand
• Signal 2?

Question 2

Polymyositis (PM)

Answer 2

• CD8 in myofiber
• CD- perivascular
• cells infiltrate IN the fasicle
• scattered necrotic fibers
• target = myofiber

Question 3

Dermatomyositis (DM)

Answer 3

• pervascular B cells and complement pores
• infiltrate AROUND/OUTSIDE fasicle
• necrotic fibers in distinct groups
• perifascular atrophy - breaking it down more
• target = blood vessels
  
  • Ig and complement deposition in vessels

Question 4

Autoantibodies

Answer 4

• ANA, antithyroid

- Anti-Jo-1

Question 5

Anti Jo-1 autoantibody

- Clinical associations
- What does it target
- mechanism of action of its target

Answer 5

Clinical associations of Jo-1
- acute onset, pumonary symptoms
- high fever, arthritis, mechanic hands, raynauds
Target:
- histidyl-transfer RNA synthetase - adds aa to tRNA
- when cells damaged, human tyrosyl tRNA syntehtase is broken into two cytokines
- IL-8 and monocyte activator
Mech of action
- viral damage to muscle
- liberates auto-antigenic aatRNA synthetase
- recruits mononuclear cells and activates innate and adaptive inflammation
- perpetuates myositis
- INF - alpha gene is turned on (activates macrophages)
- similar to INF-gamma signature in SLE