The host response to infection with microorganism and microorganism-derived molecules is characterized by the synthesis and release of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukins 1, 6 and 8 (IL-1, IL-6, and IL-8), by inflammatory cells, and by other markers of inflammation such as C-reactive protein. Inflammatory cells, such as macrophages, release these cytokines by signals transmitted from the surface of these cells after binding of pathogen-associated molecules to cell surface pattern recognition receptors known as toll-like receptors.