The New England journal of medicine
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Endemic pemphigus foliaceus, or fogo selvagem, is an autoimmune blistering skin disease caused by IgG autoantibodies to a desmosome-associated glycoprotein. We studied the IgG subclasses with autoantibody activity in serum from 29 patients with active disease and in the skin lesions of 18 patients by immunofluorescence, using IgG-subclass-specific monoclonal antibodies. The predominant disease autoantibodies present in all patients were of the IgG4 subclass. ⋯ Only IgG4 autoantibodies were detected by direct immunofluorescence, bound to the epidermis in the lesions of the mice, and by immunoelectron microscopy at the keratinocyte surface. IgG4 has previously been reported to be a blocking or protective antibody because it has poor effector functions in vitro, as compared with the other IgG subclasses. The finding that it is the pathogenic autoantibody in fogo selvagem raises the possibility that it may also be important in other autoimmune disease.
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Bicycling accidents cause many serious injuries and, in the United States, about 1300 deaths per year, mainly from head injuries. Safety helmets are widely recommended for cyclists, but convincing evidence of their effectiveness is lacking. Over one year we conducted a case-control study in which the case patients were 235 persons with head injuries received while bicycling, who sought emergency care at one of five hospitals. ⋯ In regression analyses to control for age, sex, income, education, cycling experience, and the severity of the accident, we found that riders with helmets had an 85 percent reduction in their risk of head injury (odds ratio, 0.15; 95 percent confidence interval, 0.07 to 0.29) and an 88 percent reduction in their risk of brain injury (odds ratio, 0.12; 95 percent confidence interval, 0.04 to 0.40). We conclude that bicycle safety helmets are highly effective in preventing head injury. Helmets are particularly important for children, since they suffer the majority of serious head injuries from bicycling accidents.