C1q, the classical complement pathway protein binds Hirano bodies in Pick's disease

Area of Science:

• Neuropathology
• Neuroimmunology
• Complement System

Background:

• Pick's disease is a neurodegenerative disorder characterized by the presence of Pick bodies.
• Hirano bodies are eosinophilic inclusions found in neurons, often associated with neurodegenerative conditions.
• The role of the complement system in the formation and characteristics of Hirano bodies is not fully understood.

Purpose of the Study:

• To investigate the presence and characteristics of Hirano bodies in Pick's disease.
• To examine the association of Hirano bodies with complement components and glial cells.
• To determine the immunoreactivity of Hirano bodies with specific complement pathway components.

Main Methods:

• Haematoxylin/Eosin staining for Hirano body screening in 10 Pick's disease cases.
• Immunostaining with anticomplement antibodies (C1q, C4, C3, factor B).
• Immunostaining for astrocyte marker (GFAP) and microglia marker (HLA class II CR3/43).

Main Results:

• Hirano bodies were confirmed in 9 out of 10 Pick's disease cases.
• Extracellular Hirano bodies were predominantly observed adjacent to neuronal somata in the hippocampus CA1 region.
• Hirano bodies showed intense reactivity with C1q but were unreactive with C4, C3 activation products, and factor B.
• Hirano bodies were negative for astrocyte and microglia markers.

Conclusions:

• Hirano bodies in Pick's disease exhibit strong immunoreactivity with C1q, suggesting classical complement pathway involvement.
• The study did not find evidence of association with astrocytes or microglia.
• Further investigation is required to elucidate the role of other complement components in Hirano body formation.