Methods: The IgE reactivity to rDer p 13 was analysed by ELISA using 644 sera with a positive skin prick test (SPT) to D.pteronyssinus and collected from four different hospitals in Bangkok. The allergenic activity of rDer p 13 was tested using IgE-loaded rat basophil leukaemia cells (RBL) expressing human FcεRI. The direct airway epithelial cell activation by rDer p 13 was also evaluated.
Results: Only 6% of 644 HDM-allergic patients showed IgE-reactivity to rDer p 13 whereas the IgE binding frequency to rDer p 2 reached more than 60%. In RBL assays, rDer p 13 triggered basophil degranulation but the effector activity was lower than that measured for rDer p 2. Treatment of BEAS-2B respiratory epithelial cells with rDer p 13 triggered the production of IL-8 in a concentration-dependent manner.
Conclusions: Although rDer p 13 displays allergenic activity, its weak IgE reactivity clearly confirmed that Der p 13 is a minor allergen. We hypothesized that the poor IgE binding frequency of Der p 13 is in line with the apparent very limited amount of this allergen in mite fecal pellets aqueous extracts. Nevertheless, Der p 13, through its fatty acid binding capacity, could play a role in the activation of innate signaling pathways to initiate the allergic response.