Cryosections (16 μm) of various zones immunoreacted for PGP9.5 and PLCβ2. A In zone 2 (anterior nasal cavity) few OSNs show PGP9.5-like immunoreactivity. B In zone 4 (anterior turbinate) considerably more OSNs are labelled with PGP9.5. Also, two larger apical endings (arrow) are darkly labelled (see also paragraph solitary chemosensory cells). C In the most ventral nonsensory portion of zone 3 no labelled cells occur. The apical fringe of nonsensory cilia is labelled non-specifically as is typical for nonsensory cilia. D A control section from zone 4 (anterior turbinate) where the primary antibody had been omitted shows no label at all. E PLCβ2 labels thick apical endings of few cells (arrows) in zone 2 (anterior nasal cavity) and also in F Zone 4 (anterior turbinate). Size and scarceness of the label indicates that these are SCCs.