Background: The development of allergic hypersensitivity depends on both genetic and environmental factors. Different amounts of microbial products could affect patients with atopy and different genotypes.

Objective: We aimed to evaluate the role of varying degrees of exposure to infection by Mycobacterium tuberculosis (tuberculosis) in atopic patients and analyze the association with genetic factors.

Methods: We performed CD14-159C/T genotyping in atopic patients (n=118) and healthy individuals (n=62) and recorded the following variables: rural lifestyle, exposure to persons with tuberculosis, bacille Calmette-Guérin (BCG) vaccination, tuberculin skin test (TST), skin prick test, and phenotypes of atopy. Blood samples were analyzed for soluble-CD14 (sCD14), interferon (IFN) γ, total immunoglobulin (Ig) E, and eosinophil levels. A score was used to identify the likelihood of exposure to tuberculosis.

Results: Almost all the study participants had had a BCG vaccination, and half had a positive TST result. No differences were observed between atopic patients with high/low tuberculosis scores and CD14 genotypes in terms of atopic phenotypes, allergen sensitization, and levels of total IgE, sCD14, and IFN-γ. However, the frequency of asthma was higher in atopic patients with a high tuberculosis score and was not associated
with CD14 genotypes. Eosinophil counts in blood were higher in atopic patients with a high tuberculosis score and CC+CT genotypes.

Conclusions: These results suggest that the C allele of the CD14-159C/T polymorphism has a marked effect on eosinophil levels in atopic patients with increased exposure to tuberculosis. In addition, the degree of exposure to tuberculosis in atopic patients may modify the development of asthma.

Key words: Atopy. BCG. CD14 polymorphism. Rural life. Tuberculosis