IL-1R1 (CD121a) belongs to IL-1 receptor, and binds to IL-1alpha, IL-1beta, IL-1Ra and IL-38 with comparable affinities (Kd: 0.1-1 nM)[1]. IL-1R1 regulates the transcription of multiple proinflammatory cytokines and mediates immune and inflammatory responses, including the activation of NF-kappaB and MAPK pathway[4]. I IL-1R1 Protein, Human (HEK293) is a recombinant human extracellular region of IL-1R1 (M1-T332) without any tag, which is produced in HEK293 cells.