Abstract

It is likely that the murine response to human recombinant TNF? (hrTNF?) may generate antibodies (Ab) to epitopes present in TNF? from other species. Here, we demonstrate that F5 anti-hrTNF? monoclonal antibody (mAb) recognizes feline TNF? while E8 anti-hrTNF? mAb failed to do so. In order to demonstrate that E8 and F5 mAb recognize different epitopes in the hrTNF? molecule, a constant concentration of E8 and variable concentrations of F5 were incubated with solid phase bound hrTNF?. Binding of E8 and F5 to hrTNF? was determined with anti-? and ? chain specific Ab. F5 bound equally to hrTNF? the presence or absence of E8 and the same amount of E8 bound to hrTNF?, in spite of the presence of F5. When using the E8 and F5 mAb for capturing the TNF? from the equine, canine, feline and bovine species, in supernatants of an ex vivo lipopolysaccharide (LPS)-stimulated whole blood cell culture, we only detected the feline TNF? by F5 mAb (p = 0.001). By a cytotoxic assay on L929 fibroblasts, we indeed demonstrated the feline TNF? production after the LPS stimulus. In an inhibition assay, the human and feline cytokines competed for F5, although the inhibition of native human TNF? binding to F5 was significant but only about 20% (P = 0.001). In conclusion, most likely the F5 anti-hrTNF? mAb recognizes an epitope in feline TNF?. Its immunomodulatory potential in the feline model remains to be studied.