Keywords: house dust mites; IgG2; IgG4; specific behaviour of high responders; sublingual immunotherapy; vitamin D EN house dust mites IgG2 IgG4 specific behaviour of high responders sublingual immunotherapy vitamin D 1219 1224 6 10/13/22 20221001 NES 221001 Key messages Seric vitamin D is not a predictive marker of allergy immunotherapy (AIT) efficacy. Indeed, the latter display correlated levels of serum vitamin D before treatment, on the on hand, and of allergen-specific IgG4 and IgG2 before and/or after treatment, on the other hand. As an illustration, serum levels of vitamin D before treatment were plotted against serum levels of I D. pteronyssinus i -specific IgG4, as measured in high and low responders before treatment (Figure 1D,E, respectively) and after treatment (Figure 1F,G, respectively). Moreover, statistically significant positive correlations occurred in high responders only, between, on the one hand, the serum concentration of vitamin D before treatment and, on the other hand, the serum concentrations of HDM-specific IgG4 and IgG2 before and/or after treatment (Table 1). [Extracted from the article]