Which statement about Toll-like receptors is true according to the material?

• A. They protect adult flies from infection
• B. They enhance phagocytosis
• C. They are found on all host cells
• D. They only play a role in adaptive immunity

Answer: (B)

Toll-like receptors are innate immune sensors that detect common microbial components (PAMPs) and trigger signaling that activates macrophages and dendritic cells, leading to inflammatory cytokine production and enhanced microbicidal activity. This activation directly boosts the cells’ ability to engulf and destroy pathogens, so promoting phagocytosis is the best description of their function. While TLRs were studied in Drosophila and are part of a conserved family, in mammals their primary role is rapid innate sensing and activation—not exclusive protection of flies. They are not found on every cell type, and they are crucial for initiating innate responses and shaping subsequent adaptive immunity, not only adaptive immunity.