The antibody neutralizes specific mouse interleukin 6 (IL-6). It does not cross-react with LPS (thecomponent of the bacterial cell wall which is considered responsible for the toxicity of gram-negativebacteria) and TNF-alpha nor does it block human or rat IL-6 in proliferation assays using the KD83 cellline. MP5-32C11 inhibits mouse IL-6-induced proliferation of the NFS60 myelomonocytic cell line andKD83 plasmacytoma. IL-6 is a pluripotent 20-22 kDa cytokine which plays a role in the pathophysiology ofsevere infection and regulates the immune response, acute phase reaction and haematopoiesis. IL-6 playsa critical role in B-cell differentiation to plasma cells and is a potent growth factor for plasmacytoma andmyeloma. Continuous IL-6 gene expression makes an essential contribution to a multistep oncogenesis ofplasma cell neoplasia. IL-6 is a very useful culture supplement for the generation of a high number ofantibody-producing hybridomas.