Analysis of IL-12 Receptor β2 Chain Expression of Circulating T Lymphocytes in Patients with Atopic Asthma

Th2 cell predominance relative to Th1 cells contributes to pathological immune responses in patients with atopic asthma. IL-12 is a key cytokine in the induction of Th1 cells, and downregulation of IL-12 production is reported in these patients. However, IL-12 receptor expression of their T lymphocytes has not been clarified. In this study, expression of IL-12 receptor β2 on T cells and secretion of cytokines which affect IL-12 receptor β2 expression by their PBMC were examined. We found that IL-12 receptor β2 expression of the T cells is reduced. This is partly due to the diminished production of IL-12 and enhanced secretion of IL-4 by their PBMC. IL-18 production is not significantly modulated in these patients. Furthermore, intrinsic defects of the CD4+ T cells, which reduce their IL-12 receptor β2 expression in response to IL-12 and/or IL-18 stimulation, are evident and are importantly involved in the Th1/Th2 imbalance of patients with atopic asthma.