Triggering the immune response by proinflammatory cytokines

What determines whether or not an immune response takes place? The older view that it is only the presence or absence of T cells bearing appropriate receptors that matters has been replaced by one which lays at least equal emphasis on inflammation: whether or not antigenpresenting cells become activated and secrete proinflammatory cytokines. The evidence for this view comes partly from older work on animal models of autoimmunity and tolerance, partly signs of “immunological neglect” in transgenic mice akin to “immunological privilege”, and partly from some remarkably supportive genetics. The genetics includes genome scanning for quantitative trait loci determining disease susceptibility and case/control disease associations. Migration inhibitory factor is an interesting proinflammatory cytokine which does not yet fit into this scheme. We ask but do not answer the question whether protective T cell populations are subject to the same rules of activation.