Among primary blood cells, RALDH2 expression is restricted to basophils. Western blot analysis of RALDH2 expression in different primary human cell subsets. Cells were analyzed directly or after 24 hours of culture with the stimuli indicated. All stimuli were used at a concentration of 50 ng/mL. (A) Freshly isolated (f.i.) or stimulated granulocytes were analyzed for RALDH2, GzmB, and Pim-1 expression. (B) pDCs and peripheral blood mononuclear cells (PBMCs) were probed for RALDH2, the high-affinity NGF receptor Trk, IL-3 receptor-α (IL-3R), and GzmB. Basophils, untreated or stimulated with IL-3, are included as controls. (C) Expression of RALDH2 in leptomeninges of a human embryo (embryo) in comparison with IL-3–stimulated basophils (Ba). Actin is shown as loading control.