Reduced levels of soluble CD14 in atopic children

BACKGROUND: A reduced microbial stimulation has been reported as a reason for the increasing prevalence of atopic diseases in industrialized countries. Antigen-presenting cells (APC), responding to microbial signals by pattern recognition receptors such as CD14, have an important role in the development of the Th1/Th2 balance. OBJECTIVE: We hypothesized that atopic children have a lower expression of CD14 on monocytes and lower soluble CD14 levels (sCD14). METHODS: Seventy-six children were followed prospectively from birth and signs of atopic disease were evaluated. The expression of CD14 on monocytes was analysed with flow cytometry at 0, 3, 6, 12 and 18 months. Circulating levels of sCD14 were analysed by ELISA and total IgE was analysed by fluoroenzymo immunoassay at these ages, and in a subgroup, followed up at 7 years. RESULTS: Levels of sCD14 were reduced at 7 years both in children with a current or a cumulative history of atopy compared to non-atopic children with P=0.002 and 0.001, respectively. Sensitized children with atopic symptoms had lower sCD14 at 3 and 18 months and at 7 years of age than non-atopic non-sensitized children with P=0.023, 0.039 and 0.008, respectively. CONCLUSION: The lower levels of sCD14 observed in atopic children may be a consequence of an atopic family heredity and/or atopic disease, but it may also reflect a reduced capacity to respond to microbial signals.