Image of an intraepithelial lymphocyte (IEL) from a CLIC5 mutant mouse small intestine. The CLIC (Chloride Intracellular Channel) family of proteins is expressed in a wide variety of cell types, and several isoforms are known to cycle between soluble and membranebound forms. As well as being widely expressed, the CLICs are involved in diverse functions, including tubulogenesis, immune cell activation, apoptosis and calcium handling. CLIC5 has been shown to associate with cytoskeletal proteins in placental microvilli and inner ear cells, and is required for proper maintenence of hair cell steriocilia. It has also been localized to the cytosol of human intestinal epithelial cells, though its function there remains unclear. The study in which this particular “IEL” was found, involved a search to see what function CLIC5 played in the modulation of tubulovesicles and microvillar apical membranes in the process of acid secretion. In particular, the relative amounts and structural characteristics of these two membrane types was quantified in parietal cells.