11.4: Innate Defenders Last updated Jan 3, 2021 Save as PDF 11.3B: Antigen-presenting Cells - B and T cells 11.4A: The Complement System Page ID11768 ( \newcommand{\kernel}{\mathrm{null}\,}\) Topic hierarchy11.4A: The Complement SystemThe complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism.11.4B: InterferonsInterferons (IFNs) are proteins made and released by host cells in response to the presence of pathogens.11.4C: Natural Killer CellsNatural killer cells (or NK cells) are a type of cytotoxic lymphocyte critical to the innate immune system.11.4D: Toll-Like ReceptorsToll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system as well as the digestive system.11.4E: Iron-Binding Proteins11.4F: Antimicrobial Peptides11.4G: The Complement System and Heart Disease