Club cells, neutrophils, and B cell–T cell interactions. (A) Single section from an array tomography image stack of an adult zebrafish ALO, showing an overview tangential section through the edge of an ALO with numerous club cells (magenta asterisks) in the mid-cortex. (B and C) Transmission electron micrograph of an adult zebrafish ALO, showing an individual club cell with homogeneous cytoplasm and complex, folded nucleus. Panel C shows a higher magnification image of the nucleus-containing boxed region in panel B. (D–F) Single section confocal/DIC micrographs of the ALO cortex from a Tg(gng13a:eGFP)^y709 transgenic zebrafish, with en face overview (D) and side-view (E) images of the cortex. Panel F shows the same image as panel E but with only DIC, showing that the unique club cell morphology, a large cell with a central large nucleus, is easily identifiable through DIC alone. See Video 2 for additional array tomography images of club cells. (G–G‴) Still images from a time-lapse movie showing a neutrophil Tg(lysC:DsRed)^nz50 crawling in the dermal cortex of an adult ALO (ex vivo) (see Video 7). (H–H‴) Still images from a time-lapse movie showing T cell Tg(lck:DsRed)^nz107 and B-cell Tg(cd79b:egfp)^fcc89 interactions (ex vivo) (see also Video 9). Scale bars = 20 µm (A), 5 µm (B), 1 µm (C), 25 µm (D and E), 10 µm (G and H).