Figure 1.

Primary cilia are present in human folli-cular cells. (a) Thyroid follicles exhibit numerous cilia oriented towards the colloid. (b) Primary cilia are located in the center of the apical cell surfaces (tangential section). Virtually every follicular cell displays at least one cilium (c). However, the presence of two primary cilia emerging in close proximity is not uncommon (d). Detail of the primary cilia (e). Secondary cilia of the tracheal epithelium are demonstrated as positive control (f). Double immunofluorescence staining: E-cadherin (green); acetylated α-tubulin (red); blue (nuclear counterstaining with DAPI).