PHA-induced IL-12Rβ2 mRNA expression in atopic and non-atopic children

Background IL-12 is a strong inducer of Th1 responses. Stimulation via the CD2 receptor increases IFN-gamma production and enhances the responsiveness of activated T-cells to IL-12, possibly due to an up-regulation of the signal transducing beta (2) chain of the IL-12 receptor (IL-12R beta (2)). Atopic children have a reduced Th1-like immunity and a reduced CD2 expression. Our hypothesis is that atopic individuals have a reduced function of the CD2 pathway, causing reduced responsiveness to IL-12 and decreased IFN-gamma production. Objective The aim was to study the mRNA expression of the IL-12R beta (2) chain, after stimulation via the CD2 pathway in peripheral blood mononuclear cells (PBMC), of atopic and non-atopic children, and to investigate correlations to the production of Th1 and Th2 cytokines. Materials and methods The study included 23 skin prick test positive, and 9 nonsensitized, 12-year-old children. PBMC were stimulated for 24 h with phytohemagglutinin (PHA) (2 mug/mL), which stimulates T cells through the CD2 pathway. Expression of IL-12R beta (2) mRNA was analysed by quantitative real time PCR and the cytokine production was detected with ELISA. Results Atopic and non-atopic children had similar baseline expression of IL-12R beta (2) mRNA, whereas PHA-induced IL-12R beta (2) mRNA expression was lower in atopic than in non-atopic children. The PHA-induced IL-12R beta (2) mRNA expression correlated well with the PHA-induced IFN-gamma production and with the IFN-gamma /IL-4 ratio. Conclusion PBMC from atopic children expressed less IL-12R beta (2) mRNA than non-atopic children after stimulation via the CD2 pathway (PHA). This may indicate a reduced capacity to respond to Th1-inducing stimuli in atopic children.