Persistent high plasma levels of interleukins 18 and 4 in children with recurrent infections of the upper respiratory tract

The aim of this study was to examine whether children with recurrent infections of the upper respiratory tract might have alterations in the systemic immune response to viral infections as compared with healthy control children. We quantitated plasma levels of interferon-γ, interleukin-12, interleukin-18, interleukin-4, lymphocyte subpopulations, serum immunoglobulins, and subclasses of immunoglobulin G in 30 children under the age of 6 years with recurrent infections of the upper respiratory tract, both during the acute phase of the infection and 4 weeks later, when clinical symptoms had resolved, as well as in 20 normal controls. We found elevated levels of immunoglobulin G primarily due to increased levels of immunoglobulin G 1. Moreover, significantly higher levels of interleukin-18 and interleukin-4 were noted during the acute phase of infection among children with an increased incidence of respiratory infections as compared with the controls ( P = .022 and P = .0001, respectively), while plasma levels of interferon-γ and interleukin-12 were significantly lower ( P = .034 and P = .0001, respectively) than in controls. We suggest that an imbalance between T-cell helper type-1 and T-cell helper type-2 immune responses might be responsible for the perpetuation of recurrent infections of the upper respiratory tract.