Surfactant proteins SP-A and SP-D: structure, function and receptors

Area of Science:

• Pulmonary immunology
• Innate immunity
• Molecular biology

Background:

• Surfactant proteins SP-A and SP-D are collectins crucial for lung homeostasis and immunity.
• They possess collagenous and carbohydrate-binding domains (CRDs) that interact with microbes, allergens, and dying cells.
• These proteins play diverse roles in viral neutralization, pathogen clearance, and allergic responses.

Purpose of the Study:

• To provide an updated review of the structural and functional aspects of SP-A and SP-D.
• To emphasize their roles in controlling pulmonary infection, allergy, and inflammation.
• To discuss the controversial topic of SP-A and SP-D receptor molecules.

Main Methods:

• Review of existing literature on SP-A and SP-D.
• Analysis of studies involving gene knock-out mice and murine models.
• Examination of functional characterization of cell surface receptors.

Main Results:

• SP-A and SP-D exhibit dual roles: anti-inflammatory in naive lungs and pro-inflammatory during overwhelming insults.
• The calreticulin-CD91 complex is a proposed receptor mediating anti-inflammatory effects.
• SP-A and SP-D are vital for innate and adaptive pulmonary immunity.

Conclusions:

• SP-A and SP-D are versatile immune molecules with context-dependent functions in the lung.
• Understanding their receptor interactions is key to elucidating their roles in pulmonary health and disease.
• Further research is needed to clarify the controversial aspects of their receptor binding.