Summary ihirgrd anions such as heparin. Neutrophil actirity is generally depressed by intravenous unaesthetic induction agents, hut is enhanced by 0pioid.y. Natural killer cell activity, which is invohed in immunity against tuniour cells and iGrully infbcted cells is transientlr depressed by volatile anaesthetic agents and opioids. In contrast catecholamines enhance natural killer cell activity. Whereas drcrease in inimunoglobulin levels occur peri-operaticely, this is not thought to be us a result of drugs at clinicully used concentratiows but rather due to haemodilution. Key wordsIniniune responsc .The possible effects of anaesthesia on the immune system have been discussed from as early as 1916 [I]. This review discusses how drugs commonly used in anaesthesia and intensive care may modulate immunological parameters and looks beyond currently published work to those areas likely to be of clinical importance in the near future. Excellent guidance on basic imniunopharmacology may be found in several specialist tests, for instance Dale, Foreman and Young, Trsthook of Init~iirnopharnir~cology (Blackwell Scientific Publications) [2]. Basic structure of the immune system Innutr und adaptii~e initnunit! (Fig. I )Any immune response involves recognition of an infectious agent or other foreign material and the resulting reaction against it to remove it. The natural or innate response is rapid. non-specific for the antigen and does not improve upon repeated exposure. In contrast, the adaptive response is highly specific for a particular antigen and improves upon successive exposure to that antigen, constituting a memory mechanism which protects against future encounters with the antigen. Innate immune responses are mediated by natural killer (NK) cells and phagocytic cells such as monocytes, macrophages and polymorphonuclear neutrophils which use primitive nonspecific recognition systems to bind micro-organisms, then neutralise and destroy them. Lymphocytes are central to all adaptive immune responses, specifically recognising the antigen and initiating the response to it. B-lymphocytes release antibody which specifically recognises and binds to extracellular pathogens and their products (humoral immune response). T-lymphocytes are composed of subsets termed T-helper 1 ( T H~) , The effects of opioids on NK cell activity is controversial, and depends on the experimental system studied. It has been postulated that natural killer cells have opioid receptors and it is thought that through this mechanism 8-endorphin in vitro can augment the cytolytic activity of natural killer cells-an effect which can be blocked by naloxone [5, 61. In a rat model, stress-induced endorphins were found to have an inhibitory effect on natural killer cell activity, an effect which could be mimicked by high-dose morphine and blocked by naloxone [7]. In a preliminary report, anaesthesia in patients using a high-dose fentanyl technique led to a depression in natural killer activity lasting for 3 days. This effect could be reversed in vitro by add...

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Chronic Fatigue Syndrome is a disorder which is characterised by profound fatigue together with a variety of other subjective clinical features which persist over a prolonged period of time. The aetiology remains at present uncertain and therefore rational therapeutic strategies are difficult to plan. This paper reviews currently used forms of treatment aimed at correcting the possible pathophysiological mechanisms and discusses the problems associated with the management of this condition.

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