To study the allergenic activity of Art v 1‐expressing VNP, we passively sensitized wild‐type rat basophil leukemia (RBL) cells or RS‐ATL8 cells expressing the human FcεRI44 with pooled, Art v 1‐specific mouse sera or sera of five mugwort allergic individuals, respectively, and incubated them with different doses of MA::Art v 1 VNP, Art v 1::GPI VNP, empty VNP, rArt v 1, or anti‐IgE. This evidence concerns the gene IGHE and acute basophilic leukemia.