Risk to Metropolitan police officers from exposure to hepatitis B.

Comment The increased bacterial adherence to epithelial cells found in children with vitamin A deficiency provides evidence for an additional factor that can contribute to the increased risk of infection in this disease. Nutritional deficiencies impair several host defence mechanisms, but much of the work done in the past 20 years focused on immune responses rather than physical barriers. ' This study shows that respiratory epithelial surfaces of vitamin A deficient subjects may permit increased colonisation and thus allow penetration of mucosa, leading to systemic infection. Various barriers contribute to local defence on mucosal surfaces, including mucus, glycocalix, cilia, secretory IgA, neutrophils, macrophages, and T lymphocytes. It is not clear which aspects of this barrier are affected by vitamin A deficiency. A prospective study should be done to correlate bacterial adherence to epithelial cells with morbidity. A firm cause and effect relation would be established if vitamin A supplements were found to correct the abnormal bacterial adherence.