The antibody neutralizes mouse interleukin 6 (IL-6). It does not cross-react with LPS (the component of thebacterial cell wall which is considered responsible for the toxicity of gram-negative bacteria) and TNFalphanor does it block human or rat IL-6 in proliferation assays using the KD83 cell line. MP5-32C11inhibits mouse IL-6-induced proliferation of the NFS60 myelomonocytic cell line and KD83 plasmacytoma.IL-6 is a pluripotent 20-22 kDa cytokine which plays a role in the pathophysiology of severe infection andregulates the immune response, acute phase reaction and haematopoiesis. IL-6 plays a critical role in Bcelldifferentiation to plasma cells and is a potent growth factor for plasmacytoma and myeloma.Continuous IL-6 gene expression makes an essential contribution to a multistep oncogenesis of plasmacell neoplasia. IL-6 is a very useful culture supplement for the generation of a high number of antibodyproducinghybridomas.