mRNA expression and RNA editing (2451 C-to-U) of IL-12 receptor beta2 in adult atopic patients

Abstract

Interleukin (IL)-12 activates T helper (Th) 1 cells to produce interferon (IFN)-gamma which inhibits atopic inflammation. IL-12 acts through interaction with its receptor, especially beta(2) subunit. In several studies, the low production of IFN-gamma in peripheral mononuclear cells of atopic patients on response to IL-12 stimulation has been reported. Therefore we investigated the IL-12 receptor beta(2) (IL-12R beta(2)) mRNA expression and RNA editing, nucleotide 2451 C-to-U conversion, to find the cause of low responsiveness to IL-12 in atopy. Quantitative real time PCR for mRNA expression and sequence analysis for RNA editing were performed in 80 atopic patients and 54 healthy controls. The expression of IL-12R beta(2) mRNA was significantly lower in atopic patients than healthy controls (p<0.05). In sequence analysis, RNA editing on nucleotide 2451 was not found from either atopic patients or healthy controls. In additional evaluation, there was no relationship between expression of IL-12R beta(2) mRNA and serum total IgE or blood eosinophil count. Reduced IL-12R beta(2) mRNA expression in atopic patients indicate the reduced capacity to respond to IL-12 which induce IFN-gamma production and this may contribute to Th2-skewed immune response in atopy.

Fig. 1

Melting curves of amplification products of IL-12Rβ₂ mRNA (A) and GAPDH (B). Solid arrow indicates non-specific primer-dimers product.

Fig. 2

Comparison of IL-12Rβ₂/GAPDH ratio between healthy controls (n=54) and atopic patients (n=80). The mRNA expression of IL-12Rβ₂ is significantly lower in atopic patients than healthy controls (p<0.05).

Fig. 3

Results of sequencing analysis of IL-12Rβ₂ cDNA (A) and genomic DNA (B). Both bases of nucleotide 2451 of cDNA and genomic DNA are cytosines in atopic patients and healthy controls. Arrows indicate the base composition of nucleotide 2451 on exon 13.

Fig. 4

Comparison of IL-12Rβ₂/GAPDH ratio among 3 groups divided by serum total IgE concentration. Significant difference is not found between 3 groups (one way ANOVA, p>0.05).

Fig. 5

Relationship between IL-12Rβ₂/GAPDH ratio and blood eosinophil count in atopic patients. Significant relationship between IL-12Rβ₂ mRNA expression and blood eosinophil count is not found (Spearman's correlation test, p>0.05).