title: Cytokines as mediators of graft-versus-host disease.
abstract: Cytokines are proteins produced mainly by lymphocytes in response to an antigenic stimulus. Originally identified and named on the basis of their biological activity, they are now called interleukins; together with the interferons, colony-stimulating factors and tumour necrosis factor/cachectin (TNF) they form a complex and overlapping network of communication between immunocompetent cells. Cytokines play a central role in T cell activation, and interleukin 2 and interferon gamma in particular are involved in the expression of graft-versus-host disease after bone marrow transplantation. Recent studies suggest that TNF is also implicated: the gene encoding TNF is situated close to the MHC gene in both mice and humans, and TNF is able to up-regulate constitutively expressed class II antigen and, with interferon gamma, to induce class II expression in previously normal cells. Bacterial lipopolysaccharide (endotoxin) is a powerful stimulus to TNF, and TNF production may be the mechanism underlying the longstanding observations on the role of the bacterial microflora of the gut in graft-versus-host disease.
mesh_terms: D000818:Animals; D001685:Biological Factors / Q000276:immunology*; D016026:Bone Marrow Transplantation; D016207:Cytokines; D006086:Graft vs Host Disease / Q000209:etiology*; D006801:Humans; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: D001685:Biological Factors; D016207:Cytokines; D014409:Tumor Necrosis Factor-alpha