Human interleukin 1β (IL-1β) is a 17 kDa protein which is produced by various cells. IL-1β has multiple functions including local inflammation. Following bacterial or immunoglobulin ligation of monocyte/macrophage CD14 (the LPS receptor) 17 or CD64 (the IgG receptor), IL-1β can be released into a local environment. Within this environment, IL-1β impacts a number of cells, facilitating mononuclear infiltration into an area of early inflammation. IL-1β also induces expression of itself in newly arriving monocytes. In terms of other pro-inflammatory molecules, IL-1β apparently is needed for the efficient production of IFN-γ. On resident NK cells, IL-1β apparently works in conjunction with macrophage-derived IL-12 to induce IFN-γ secretion, resulting in an IFN-γ induced activation of macrophages. Finally, IL-1β also induces the expression of MMPs from resident fibroblasts. This can have at least two effects: first extracellular matrix degradation can facilitate monocyte migration, and second, MMPs are known to degrade IL-1β, thus down-modulating the local inflammatory response initiated by IL-1.