Final answer:
SP-A, an opsonin, is recognized by either Complement receptor 1 or Fc receptor on phagocytic cells, facilitating pathogen recognition and phagocytosis as part of the innate immune response.
Step-by-step explanation:
SP-A (opsonin) can be recognized by specialized receptors on the surface of phagocytic cells. Specifically, SP-A can either be recognized by Complement receptor 1 (CR1) or Fc receptor. These receptors are part of the innate immune response, aiding in the process of opsonin-dependent phagocytosis. When opsonins like SP-A coat a pathogen, phagocytic cells such as macrophages and neutrophils use their receptors to bind and engulf the pathogen. This is an example of how the innate immune system recognizes and eliminates pathogens.