IL18 and hemophagocytic syndrome: The pathogenesis of HLH depends on a vicious circle: not only Toll-like receptors of innate immunity cells (primarily stimulated by pathogen-associated molecular patterns), but also their receptors for IL-1 and IL-18 (which are stimulated by excess levels of these interleukins) can, at the post-receptor level, activate the same intracellular instruments (myeloid differentiation primary-response protein 88 (MyD88), and IL-1R-associated kinase (IRAK) proteins).