Final answer:
The primary function of β-defensins is to make microbes more susceptible to ingestion by phagocytes by attaching to them and acting as opsonins. They are part of the innate immune system and serve as antimicrobials directly against various pathogens.
Step-by-step explanation:
The primary function of β-defensins in response to microbes is to attach to microbes to make them more susceptible to ingestion by phagocytes. β-defensins are small antimicrobial peptides produced by cells as part of the innate immune system. When expressed on the skin, mucous membranes, and other epithelia, they protect against microbial invaders. Moreover, β-defensins contribute to the immune response by acting as antimicrobials directly against a broad spectrum of pathogens, including bacteria, fungi, and some viruses, thereby inhibiting their growth and survival.
β-defensins function as opsonins, which means they cover the surface of a pathogen, marking it for destruction by immune cells such as macrophages, dendritic cells, and neutrophils. This tagging allows for the immune cells to better recognize, bind, and ultimately engulf the pathogens through the process of phagocytosis. This tagging action is analogous to antibodies binding to antigens on the surface of bacteria, as mentioned in relation to opsonization in Figure 18.8.