METHODS: In preliminary experiments, cultured LAD2 cells were incubated overnight with biotinylated human IgE. Cells were washed and then incubated with 1, 10, 100, 1000 nM tofacitinib for 1 hour. FcepsilonRI crosslinking was next performed with streptavidin, and degranulation monitored by the release of beta-hexosaminidase (b-Hex). LAD2 cells were also incubated with tofacitinib followed by stimulation with PMA, degranulation and release of b-Hex. The effect on PgD2 production was measured 30 minutes following IgE mediated mast cell activation.
RESULTS: In LAD2 cells, b-Hex release following FcepsilonRI crosslinking or PMA stimulation remained consistently high (50-60%) in the presence of tofacitinib with no dose-response reduction in degranulation. Similarly, tofacitinib had no effect on PgD2 release.
CONCLUSIONS: The JAK kinase inhibitor tofacitinib had no effect on LAD2 human mast cell degranulation or PgD2 production. Additional experiments are underway including an examination of the effects of tofacitinib on LAD2 cytokine production, adhesion and proliferation.