NOD2 triggers an interleukin-32-dependent human dendritic cell program in leprosy

Area of Science:

• Immunology
• Infectious Diseases
• Cell Biology

Background:

• The innate immune system utilizes multiple pattern recognition receptors (PRRs) to detect microbial ligands.
• Understanding how distinct PRR activation influences host responses is crucial for developing effective treatments for infectious diseases.

Purpose of the Study:

• To investigate whether distinct PRR activation pathways trigger common or specific host responses.
• To elucidate the role of nucleotide-binding oligomerization domain-containing protein 2 (NOD2) and interleukin-32 (IL-32) in leprosy pathogenesis.

Main Methods:

• Monocyte activation via NOD2 and Toll-like receptor 2/1 (TLR2/1) was compared.
• Interleukin-32 (IL-32) dependency for dendritic cell (DC) differentiation was assessed.
• Antigen presentation capacity of DCs was evaluated using CD8+ T cells.
• Expression of NOD2, IL-32, and CD1b+ DCs in leprosy patients was correlated with clinical presentation.

Main Results:

• NOD2 activation, unlike TLR2/1 activation, preferentially induced monocyte differentiation into DCs via an IL-32-dependent mechanism.
• IL-32 alone was sufficient to induce rapid monocyte differentiation into highly efficient antigen-presenting DCs.
• NOD2, IL-32 expression, and CD1b+ DC frequency correlated with limited leprosy disease.
• Recombinant IL-32 restored NOD2-induced DC differentiation in patients with progressive leprosy.

Conclusions:

• The NOD2-ligand-induced, IL-32-dependent DC differentiation pathway is a specific host defense mechanism against microbial infections.
• This pathway plays a critical role in controlling leprosy and may represent a therapeutic target.