Interleukin-1 receptor antagonist (IL-1RA) is composed of three isoforms, one secreted (sIL-1Ralpha/IL-1Ralpha1), two intracellular (IL-1Ralpha2/IL-1Ralpha3) and produced by monocytes, tissue macrophages, Langerhans cells, dendritic cells, T and B cells, natural killer (NK) cells, large granular lymphocytes (LGL), vascular endothelium, smooth muscle, fibroblasts, thymic epithelia, astrocytes, microglia, glioma cells, keratinocytes, and chondrocytes. It is upregulated by IL-1beta, IL-4, IL-6 and downregulated by glucocorticoids. The Poly5095 polyclonal antibody reacts with human interleukin-1 receptor antagonist (IL-1RA).