Which cells respond to bacterial PAMPs via Toll-like receptors and coordinate early innate responses?

• A. B cells
• B. Eosinophils
• C. T cells
• D. Macrophages and dendritic cells

Answer: (D)

Toll-like receptors detect bacterial components and trigger rapid innate defenses by producing inflammatory mediators and activating antigen presentation. Macrophages and dendritic cells are best suited for this role because they express a broad array of TLRs on their surfaces and in endosomes. When they sense bacterial PAMPs like LPS, peptidoglycan, or flagellin, they release cytokines such as TNF-α, IL-1, and IL-6 and secrete chemokines that recruit neutrophils and promote inflammation, helping to contain the infection. Dendritic cells, in particular, not only orchestrate early inflammation but also mature and travel to lymph nodes to present antigen to naive T cells, bridging innate detection with the adaptive immune response.

B cells and T cells are central to adaptive immunity, responding after antigen presentation and antigen-specific activation, rather than driving the initial innate response through TLR sensing. Eosinophils are more involved in parasite defense and allergic responses, not the primary early innate coordination in bacterial infections.