Allergies, Asthma, and IL-10

Abstract

MICROBIOLOGY/IMMUNOLOGY The increasing prevalence of allergic responses, such as asthma and eczema, among children in developed countries, has been explained by their reduced likelihood of exposure to bacterial and viral pathogens. These infections are thought to shift the type of immunity towards a T helper 1 (TH1) cell response, which leads to the elimination of the pathogens, and to reduce the expression of TH2 cytokines, which are associated with allergy. In less-developed tropical countries, infections with parasitic worms (helminths) are very common in children. Paradoxically, such children exhibit few allergies even though immune responses to worms are of the TH2 type. In a study of Gabonese children harbouring various helminths, but otherwise vaccinated against common childhood infections, van den Bigelaar et al . measured a heightened ability to produce interleukin-10 (IL-10). This is an anti-inflammatory cytokine that suppresses allergic reactions, even in the presence of the TH2 cytokines and IgE antibodies generated by the response to infection. Consistent with this result is the observation that the lung macrophages of asthmatic patients are relatively deficient in producing IL-10. — CA Lancet 356 , 1723 (2000).