On the role of tumor necrosis factor and receptors in models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease.

The specific role of the tumor necrosis factor (TNF)/TNF receptor (TNFR) system in disease pathogenesis still remains an unresolved puzzle. Recent studies in transgenic and knockout animals, where the pathogenic influence of genetically perturbed TNF expression has been evaluated, indicate that several pathways of TNF/TNFR action may contribute independently or in concert to initiate, promote or downregulate disease pathogenesis. Evidently, organ-specific inflammatory or autoimmune pathology may ensue due to sustained activation by TNF of innate immune cells and inflammatory responses, which may consequently lead to tissue damage and to organ-specific chronic pathology. However, more cryptic functions of this molecule may be considered to play a significant part in the development of TNF-mediated pathologies. Direct interference of TNF with the differentiation, proliferation or death of specific pathogenic cell targets may be an alternative mechanism for disease initiation or progression. In addition to these activities, there is now considerable evidence to suggest that TNF may also directly promote or downregulate the adaptive immune response. It is therefore evident that no general scenario may adequately describe the role of TNF in disease pathogenesis. In this article, we aim to place these diverse functions of TNF/TNFRs into context with the development of specific pathology in murine models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease.