Description_x000D_ General description_x000D_ Interleukin-1 (IL-1), originally known as Lymphocyte Activating Factor (LAF), activates T cells and lymphocytes, which then proliferate and secrete interleukin-2.1 IL-1 is primarily released from stimulated macrophages and monocytes, but is also released from several other cell types,2 and is thought to play a key role in inflammatory and immune responses.3 Other synonyms for IL-1 include: Endogenous Pyrogen (EP), Mitogenic Protein (MP), Helper Peak-1 (HP-1), T Cell Replacing Factor III (TRF III or TRFH), B cell Activating Factor (BAF) and B Cell Differentiation Factor (BDF).4 The two closely related agents, Interleukin-1α (IL-1α) and Interleukin-1β (IL-1β) bind to the same cell surface receptor, elicit nearly identical biological responses and yet share 25% homology in their amino acid sequence. Recombinant rat IL-1β is a 17.3 kDa protein containing 153 amino acid residues._x000D_ Physical form_x000D_ Lyophilized from a 0.2 μm filtered buffered solution._x000D_ Analysis Note_x000D_ The biological activity is measured in a cell proliferation assay using murine D10S cells._x000D_ Citation_x000D_ 1. Gery, I., et al., J. Exp. Med., 136, 128 (1972)._x000D_ 2. Oppenheim, J. J., et al., Immunol. Today, 7, 45 (1986)._x000D_ 3. Durum, S. K., et al., Annu. Rev. Immunol., 3, 263 (1985)._x000D_ 4. Aarden, L., et al., J. Immunol., 123, 2928 (1979)._x000D_ 5. Symons, J., et al., Lymphokines and Interferons, A Practical Approach, Clemens, M., et al., (eds.), IRL Press, Oxford (1987).