IL-6 is an important mediator of
fever. It is capable of crossing the
blood-brain barrier and initiating synthesis of protaglandings in the
hypothalamus, thereby changing the body's temperature setpoint. In muscle and fatty tissue, IL-6 stimulates energy mobilization that leads to increased body temperature. IL-6 can be secreted by
macrophages in response to specific microbial molecules, referred to as
pathogen-associated molecular patterns (
PAMPs). These PAMPs bind to an important group of detection molecules of the
innate immune system, called
pattern recognition receptors (PRRs), including Toll-like receptors (
TLRs). These are present on the cell surface and intracellular compartments and induce intracellular signaling cascades that give rise to inflammatory cytokine production.IL-6 stimulate the production of
neutrophils (a common cell in NMO) in the bone marrow. It supports the growth of
B cells and is antagonistic to regulatory T cells.
In addition to the membrane-bound receptor, a soluble form of IL-6R (sIL-6R) has been purified from human serum and urine. Many neuronal cells are unresponsive to stimulation by IL-6 alone, but differentiation and survival of neuronal cells can be mediated through the action of sIL-6R. The sIL-6R/IL-6 complex can stimulate neurites outgrowth and promote survival of neurons and, hence, may be important in nerve regeneration through remyelination.