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Donald K. Milton, MD and Diane R. Gold, MD Background: Endotoxins, also known as lipopolysaccharides, are part of the outer membrane of the well wall of Gram-negative bacteria. Inhalation of endotoxin has been implicated in asthma and other respiratory diseases and has been shown to cause chest tightness, wheezing, and difficulty in breathing. Contrary to these adverse effects, infant exposure to low levels of endotoxin has been proposed as a protective factor against allergy and increased immune responses to allergens. Studies have shown that the endotoxin dose and the timing of the exposure influence the nature of the immune response. These findings, although controversial, indicate that early life is a critical time during which endotoxin exposure might reduce the risk of subsequent allergy through its effects on innate immunity and downstream regulation of inflammatory products. Advance: Researchers at the Harvard School of Public Health tested whether early life endotoxin exposure, judged by measuring endotoxin levels in house dust, is associated with allergen-induced inflammatory mediator production and proliferation responses of peripheral blood mononuclear cells isolated from infants with a parent with a history of physician diagnosed asthma or allergy. They found that higher levels of endotoxin were associated with decreased interleukin 13 levels in response to several common household allergens. Implications: Household endotoxin exposure was associated with decreased production of the t-helper cell cytokine interleukin 13. The results of this study are consistent with the hypothesis that early life exposure to endotoxin protects against allergic diseases and allergy later in life. Citation: Abraham JH, Finn PW, Milton DK, Ryan LM, Perkins DL, Gold DR. Infant home endotoxin is associated with reduced allergen-stimulated lymphocyte proliferation and IL-13 production in childhood. J Allergy Clin Immunol. 2005 Aug;116(2):431-7. |
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