LIF

Leukemia inhibitory factor (LIF) is a pleiotropic lymphoid factor belonging to the interleukin-6 family of cytokines. It was initially described as a factor inhibiting the proliferation of myeloid leukemia cells and inducing their differentiation into macrophages. Other activities of LIF include inhibition of adipogenesis and roles in cholinergic neuron differentiation, hematopoeisis, inflammation and bone metabolism. LIF inhibits the differentiation of embryonic stem cells, it is therefore important in ES cell culture. Human and mouse LIF share 78% amino acid homology, the human version is equally active on human and mouse cells but murine LIF is not active on human cells.

Produced in the endosperm tissue of barley grain (Hordeum vulgare).

PBS pH 7.2, sterile filtered through 0.2 µm filter.

Greater than 95% by SDS-PAGE gel analysis.

Note: Always centrifuge the vial before opening. It is recommended to reconstitute the lyophilized protein in sterile buffered saline to a concentration of no less than 100 µg/ml. For long term storage of the reconstituted solution it is recommended to add a carrier protein (0.1% HSA or BSA).

The lyophilized protein, though stable at room temperature for few weeks, is best stored at -20°C. Reconstituted protein should be used immediately or stored in working aliquots at -20°C. Avoid repeated freeze-thaw cycles.

The bioactivity of ISOkine human LIF was determined by its ability to induce proliferation of TF-1 cells in a dose dependent manner.

The ED50 value for this effect is <0.3 ng/ml corresponding to specific activity of >3.3 x 10e6 U/mg.

We recommend that the optimal concentration for each specific application be determined by an initial dose-response assay. Each batch of ISOkine growth factor is tested for bioactivity and verified to have comparable activity to a commercial source.

Endotoxin level is less than 0.005ng per µg of ISOkine product (0.05EU/µg).

Purified ISOkine product carries no pyrogenic or pro-inflammatory contaminants, as assayed with monocyte activation test using Human 10-plex Cytokine Assay measuring IL-6, TNF-alpha and IL-1 beta induction. ** Ref. The Blood Bank, University Hospital of Iceland, Reykjavik, Iceland

Recombinant human LIF contains 180 amino acids and a 16 a.a. histidine-based tag for a total length of 196 a.a. and has a predicted molecular mass of 21.8 kDa. As a result of glycosylation, the recombinant protein migrates with an apparent molecular mass of 25-30 kDa in SDS-PAGE.