The secretion of IL-1β and options for release

Unlike most cytokines, IL-1β lacks a secretory signal sequence raising the question of how is this cytokine processed and delivered outside the producing cells. After the seminal observation that IL-1β is actively secreted by human monocytes through a route alternative to the classic endoplas mic reticulum–Golgi, several different pathways have been proposed for IL-1β secretion in different cell types and culture conditions, some of which are unique to macrophage cell lines. Here we describe the most credited of these pathways. In particular, we will focus on IL-1β secretion from primary human blood monocytes. In fact, although data from macrophages or macrophage cell lines are predominant, secretion of IL-1β by monocytes is the most clinically relevant.