Mycobacterium leprae is the only known pathogen that infects peripheral nerves and Schwann cells. What is the receptor through which M. leprae invades Schwann cells and causes nerve damage?

• A CD4 receptor on T lymphocytes
• B ErbB2 receptor (HER2) on Schwann cells via laminin-2 binding ✓
• C CR3 (complement receptor 3) on macrophages only
• D TLR9 on dendritic cells triggering axonal degeneration

Explanation

M. leprae binds to the G domain of laminin-α2 (merosin) present in the basal lamina of Schwann cells. The laminin-α2–M. leprae complex binds to the ErbB2–ErbB3 heterodimeric receptor on Schwann cells and α-dystroglycan, mediating Schwann cell demyelination. Additionally, M. leprae PGL-I (phenolic glycolipid-1) binds laminin-2, facilitating axonal invasion. This unique tropism for Schwann cells causes the peripheral sensory and motor nerve damage characteristic of leprosy. CR3 facilitates macrophage entry but is not the primary Schwann cell receptor. TLR9 recognises bacterial DNA — not a mechanism of nerve invasion.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.