LIF: lots of interesting functions.

Leukaemia inhibitory factor (LIF) is one of a growing number of cytokines that cannot be readily categorized according to its functions. Rather, these pleiotropic hormones have diverse and often overlapping effects on a multitude of cell types: for example, LIF can inhibit the differentiation of embryonal stem cells on one hand and induce the differentiation of M1 leukaemic cells on the other. Recent work has shed light on the physiological effects of LIF, how these are limited, and the biochemical and biological properties of LIF and its receptor.