Question

Where is surfactant proteins aka opsonins (SP-A and SP-D) secreted from and what do they do?

a) Secreted from alveolar cells; enhance phagocytosis of microbes
b) Secreted from goblet cells; neutralize toxins
c) Secreted from mast cells; promote vasodilation
d) Secreted from neurons; regulate neurotransmitter release

Answer 1

Surfactant proteins SP-A and SP-D are secreted from type II alveolar cells and function to enhance phagocytosis of microbes by marking them for destruction, which complements the role of alveolar macrophages in removing pathogens and debris.

Step-by-step explanation:

Surfactant proteins, specifically SP-A and SP-D, are secreted from type II alveolar cells within the lungs. These proteins play a crucial role in the body's immune defense by enhancing phagocytosis of microbes. Their opsonizing action marks pathogens for destruction, making it easier for phagocytes like macrophages and neutrophils to recognize, bind, and engulf them. These surfactant proteins thus contribute to the immune system by assisting in the removal of pathogens and debris from the lungs.

Alveolar macrophages, which are also found in the lungs, have a different, yet complementary role. Their primary function is to remove pathogens and debris, maintaining pulmonary hygiene. While they do not secrete surfactant proteins, they are a crucial part of the lung's immune system.