Leukemia Inhibitory Factor (LIF) is a lymphoid factor which promotes long-term maintenance of pluripotent embryonic stem cells by suppressing spontaneous differentiation. Leukemia Inhibitory Factor (LIF) has a number of other functions including cholinergic neuron differentiation, bone and fat metabolism, mitogenesis of certain factor dependent cell lines and promotion of megakaryocyte production in vivo. Human and Mouse LIF exhibit a 78% identity in its amino acid sequence. Human LIF is an approximate 20 kDa protein containing 181 amino acid residues and is active on both human and mouse cells. Murine LIF is approximately 1000 fold less active on human cells, than hLIF. The protein is manufactured using all non-animal reagents.