Cell experiment:

CD4+ T Cell cytokine stimulation assay is performed. T cells are purified from peripheral blood mononuclear cells from human donors. Equal numbers of cells are incubated for 1 hr with JAK inhibitors (FM381) (0, 10, 50, 100, 300 nM) or DMSO control and stimulated with cytokines for 30 min. The cells are lysed, and the proteins are separated via PAGE and transferred to a polyvinylidene fluoride membrane. The proteins of interest are blotted with specific antibodies and visualized with an infrared imaging system[1].

FM-381 is a highly potent and JAK3-selective janus kinase (JAK) inhibitor (IC50 = 127 pM/JAK3, 52 nM/JAK1, 346 nM/JAK2, 459 nM/TYK2 by radiometric assay; [ATP] = 10 μM) that targets JAK3 gatekeeper (GK) Cys909 for a reversible covalent interaction, exhibiting much reduced or little potency against a panel of 409 other kinases. FM-381 is >3-fold more potent than the JAK1/3 inhibitor Tofacitinib (IC50 = 292 pM/JAK3, 496 pM/JAK1, 2.2 nM/JAK2, 8.9 nM/TYK2 by radiometric assay; [ATP] = 10 μM) in blocking JAK1/JAK3-mediated STAT5 phosphorylation in human CD4+ T-cells upon IL-2 stimulation (ECmax ~100 nM with FM-381), while being ineffective (up to 1 μM) against JAK3-independent STAT1/3 phosphorylation following IL-6 or TNFα stimulation.

Reference

[1].http://www.thesgc.org/chemical-probes/FM-381