How do genetics and environmental factors influence a child’s susceptibility to asthma?

Updated: Jan 07, 2019
  • Author: Michael J Morris, MD, FACP, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

Evidence suggests that the prevalence of asthma is reduced in association with certain infections (Mycobacterium tuberculosis, measles, or hepatitis A); rural living; exposure to other children (eg, presence of older siblings and early enrollment in childcare); and less frequent use of antibiotics. Furthermore, the absence of these lifestyle events is associated with the persistence of a Th2 cytokine pattern. Under these conditions, the genetic background of the child, with a cytokine imbalance toward Th2, sets the stage to promote the production of immunoglobulin E (IgE) antibody to key environmental antigens (eg, dust mites, cockroaches, Alternaria, and possibly cats). Therefore, a gene-by-environment interaction occurs in which the susceptible host is exposed to environmental factors that are capable of generating IgE, and sensitization occurs.

A reciprocal interaction is apparent between the 2 subpopulations, in which Th1 cytokines can inhibit Th2 generation and vice versa. Allergic inflammation may be the result of an excessive expression of Th2 cytokines. Alternatively, studies suggest the possibility that the loss of normal immune balance arises from a cytokine dysregulation in which Th1 activity in asthma is diminished. [23]

In addition, some studies highlight the importance of genotypes in children's susceptibility to asthma and response to specific antiasthma medications. [24, 25, 26, 27]


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