永利娱乐场在线:Parasites may reduce relapse in MS patients

日期:2019-03-02 09:02:04 作者:覃妁该 阅读:

By Linda Geddes Parasitic worms may have their uses after all. The bugs could alter the course of autoimmune diseases like multiple sclerosis (MS), a new study suggests Previous studies have suggested that parasites can influence the progression of autoimmune diseases in animals. To test whether this was also the case in humans, Jorge Correale and Mauricio Farez at the Raûl Carrea Institute for Neurological Research in Buenos Aires, Argentina, spent four-and-a-half years following the disease progression of 24 people with MS. Half of the patients had recently shown symptoms of parasitic infection, while the remaining 12 were otherwise healthy controls. Every three months the patients were checked for disease activity and any worsening of symptoms, and during the final 18 months of the study their blood was checked for immune cell activity. Those infected with parasites had fewer relapses, and less overall deterioration of their condition than uninfected people with MS. There were just three relapses in the parasite group in total compared with 56 relapses in the uninfected group. “This is the first direct evidence that parasites might be relevant to protection from an autoimmune disease,” says Graham Rook, an immunologist at University College London, UK, who was not involved in the study. The findings mirror observations of a decreased incidence of allergies in Vietnamese children who are infected with parasites compared with uninfected children (see Intestinal worms may not be totally bad news). They also shed further light on the so-called “hygiene-hypothesis” of allergic disease, which proposes that allergies have become more common in recent decades because we are exposed to fewer infections as children. Bacterial and viral infections trigger a subset of immune cells called TH1 cells, while a different subset called TH2 cells mediate allergies. The assumption was that in the absence of micro-organisms, the balance tipped towards TH2 cells, meaning people experienced more allergies. However, autoimmune diseases have also risen steadily in developing countries in recent decades, and these are driven by TH1 cells. The answer to what is driving this increase in allergies and autoimmune disease may lie with a different subset of immune cells called regulatory T (Treg) cells, which regulate both TH1 and TH2 responses. Correale showed that these were elevated in patients with both parasitic infections and MS, but not in MS sufferers with no infection. One hypothesis that is gaining growing acceptance is that certain bacteria and parasites – which have lived alongside humans for millennia – have gradually developed ways of stimulating Treg cells to dampen down the immune system, enabling them to survive in the body for longer. With modern standards of hygiene these “old friends” are gone and Treg cells are consequently less active, meaning the TH1 and TH2 cells go into overdrive, triggering allergies and autoimmune diseases. Researchers have been developing drugs that interfere with Treg cell activity. It was one such drug for rheumatoid arthritis that triggered the catastrophic immune reaction in six human volunteers during a clinical trial at Northwick Park hospital, London, in March 2006 (see One drug trial, six men, disaster). Theoretically, parasites might provide an alternative mechanism for dampening down immune responses – other groups are already experimenting with parasite eggs as a means of treating inflammatory bowel disease. However, Correale cautions that parasites may also induce different regulatory mechanisms other than just “upregulating” Treg cells – and parasite infections are often disadvantageous to health. “A better knowledge of the immune response during autoimmunity and parasite infection will allow us to select the best strategy for treatment,” he says. Journal reference: Annals of Neurology (DOI: