IL-22 mRNA in peripheral blood mononuclear cells from allergic rhinitic and asthmatic pediatric patients.

T helper (T(H) )-17 lymphocytes are characterized by the expression of many regulatory cytokines, including IL-17A and IL-22, but at present no clinical data are available on the expression of these cytokines in peripheral blood mononuclear cells (PBMC) from allergic asthmatic and rhinitic (AR) children. The aim of this study was to investigate a possible relationship between IL-22 and IL-17A mRNAs and clinical parameters in seroatopic, AR, and asthmatic children. The study, conducted during the pollen season, included 18 healthy and 18 allergic (n=9 asthmatic and n=9 rhinitic) children. Serum total and specific IgE, eosinophil count, and skin prick test were performed; in addition, IL-22 and IL-17A mRNA levels were detected in PBMC from healthy and allergic subjects by quantitative real-time PCR. Despite the absence of the mRNA for the IL-17A cytokine, IL-22 expression was found in PBMC from asthmatic patients, with increased IL-22 mRNA levels in patients with chronic severe respect to those with moderate asthma. A positive correlation between IL-22 mRNA and serum total IgE levels was found in asthmatic children. In addition, higher IL-22 and IL-17A mRNA levels were detected in both AR and asymptomatic seroatopic children, compared to healthy individuals, and a correlation between IL-22 and IL17A mRNA and serum total IgE levels was demonstrated. Moreover, the mRNA level of retinoic acid-related orphan receptor C, the T(H) 17 transcription factor, was found to be increased in AR but not in asthmatic patients. This study provides the first evidence that IL-22 mRNA might be expressed in chronic severe asthmatic and AR children. The expression of IL-22 and IL-17A mRNAs in asymptomatic monosensitized seroatopic children suggests a role of these cytokines in the early events involved in the development of these allergic diseases.