TNF and type 1 diabetes mellitus: The modified cells were then exposed to proinflammatory cytokines mimicking the pathogenic inflammatory beta cell microenvironment of pancreatic islet in type 1 diabetes, i.e. IFNγ/IL1β or IFNγ/IL1β/TNFα and analysed for endogenous XBP1 splicing by qPCR or light emission in cell lysates.