Journal oflmmunological Methods, 160 (1993) 267-271 267 © 1993 Elsevier Science Publishers B.V. All rights reserved 0022-1759/93/$06.00 JIM06657 Improved bioassay for the detection of porcine tumor necrosis factor using a homologous cell line: PK(15) Giuseppe Bertoni, Peter Kuhnert, Ernst Peterhans and Urs Pauli Institute of Veterinary I, Trology, University of Bern, Liinggass-Str. 122, CH-3012 Bern, Switzerland (Received 17 August 1992, revised received 16 November 1992, accepted 30 November 1992) Close similarities of various physiological parameters makes the pig one of the preferred animal models for the study of human diseases, especially those involving the cardiovascular system. Unfortunately, the use of pig models to study diseases such as viral hemorrhagic fevers and endotoxic shock syndrome have been hampered by the lack of the necessary immunological tools to measure important immunoregula- tory cytokines such as tumor necrosis factor (TNF). Here we describe a TNF-bioassay which is based on the porcine kidney cell line PK(15). Compared to the widely used murine fibroblastoid cell line L929, the PK(15) cell line displays a 100-1000-fold higher sensitivity for porcine TNF-a, a higher sensitivity for human TNF-a, and a slightly lower sensitivity for murine TNF-a. Using a PK(15) bioassay we can detect recombinant TNF-a as well as cytotoxic activity in the supernatants of lipopolysaccharide (LPS)-activated porcine monocytes at high dilutions. This suggests that the sensitivity of the test should permit the detection of TNF in biological specimens such as pig serum. Key words: Tumor necrosis factor, porcine; Bioassay; Septic shock Introduction Tumor necrosis factor (TNF)-a and -13 are closely related cytokines. They bind to the same receptors (TNF-R55 and TNF-R75) and trigger partly identical and partly different biological re- actions (Aggarwal, 1990; Fiers, 1991). TNF-a and Correspondence to: U. Pauli, Institute of Veterinary Virol- ogy, L~inggass-Str. 122, CH-3012 Bern, Switzerland. Abbreviations: ASF, African swine fever; EMEM, Eagle's minimal essential medium; FCS, fetal calf serum; LPS, lipopolysaccharide; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-di- phenyltetrazolium bromide; OD, optical density; PBMC, pe- ripheral blood mononuclear cells; PBS, phosphate-buffered saline; TNF, tumor necrosis factor; rhTNF, recombinant hu- man TNF-a; rmTNF, recombinant murine TNF-a; rpTNF, recombinant porcine TNF-~. -/3 play a central role in the host inflammatory response against viral, bacterial and parasitic in- fections (Beutler and Cerami, 1989). TNF either alone or in association with other cytokines such as IL-1, IL-6 and interferons, have been impli- cated in the pathogenesis of different diseases such as septic shock, cerebral malaria and possi- bly rheumatoid arthritis (Tracey et al., 1987; M~innel et al., 1987; Cerami and Beutler, 1988; Grau et al., 1987; Keffer et al., 1991). It has been suggested that TNF-a could also play a pivotal role in the pathology of certain viral diseases such as African swine fever (ASF) and hog cholera (Peterhans et al., 1988). These are hemorrhagic diseases of pig and may serve as potential models for similar disorders in humans. In order to develop a pig model to investigate the role played by TNF-o~ in hemorrhagic viral