IL-4 and IL-13 mRNA real-time PCR quantification on whole blood to assess allergic response.

Although routinely used in clinical practice, skin prick tests and serum specific IgE often fail to distinguish between IgE-sensitization and symptomatic IgE-mediated allergy. There is therefore a need for new laboratory tests relating allergic symptoms to the offending agent. In this way, we evaluated the diagnostic reliability of a new whole blood quantitative real-time PCR assay for IL-4 and IL-13 mRNAs. We compared the response of cat allergic patients and non-cat allergic controls upon anti-IgE and cat allergen (Fel d1) stimulation of whole blood. Allergen addition led to a significant increase of IL-4 and IL-13 mRNAs in allergic patients compared to non-allergic controls (p<0.0001). Both cytokine mRNA levels were strongly correlated and peaked within 2 h after Fel d1 or anti-IgE addition. This rapid increase as well as purification experiments led us to the conclusion that basophils represent an important if not the main source of both transcripts in this setting. The effect was allergen-specific since not observed when stimulating blood from cat allergic patients with birch pollen. Interestingly, we found that IFN-gamma mRNA, contrary to IL-4 mRNA, reached higher levels in response to Fel d1 with control individuals than with patients allergic to cat. This study shows that whole blood real-time PCR is a valuable method for IL-4 and IL-13 mRNA measurement after in vitro allergen challenge. We suggest that it might be useful, complementing conventional markers, for the diagnosis and the follow-up of allergic diseases. Further assessments are required to evaluate the clinical potential of this technique.