Tonofibrils are cytoplasmic protein structures in epithelial tissues that converge at desmosomes and hemidesmosomes.[1] They consist of fine fibrils in epithelial cells that are anchored to the cytoskeleton.[2] They were discovered by Rudolf Heidenhain, and first described in detail by Louis-Antoine Ranvier in 1897.[3]


Tonofilaments are keratin intermediate filaments that makes up tonofibrils in the epithelial tissue. In epithelial cells, tonofilaments loop through desmosomes. Electron microscopy has advanced now to illustrate the Tonofilaments more clearly.[1]

The protein filaggrin is believed to be synthesized as a giant Precursor protein, profilaggrin (>400 kDA in humans). When the filaggrin binds to keratin intermediate filaments, it causes aggregation in macrofibrils.[2]


  1. ^ a b "tonofibril" at Dorland's Medical Dictionary
  2. ^ a b Sandilands, Aileen; Sutherland, Calum; Irvine, Alan D.; McLean, W. H. Irwin (2009-05-01). "Filaggrin in the frontline: role in skin barrier function and disease". J Cell Sci. 122 (9): 1285–1294. doi:10.1242/jcs.033969. ISSN 0021-9533. PMC 2721001. PMID 19386895.
  3. ^ Charles, Arwyn; Smiddy, F. G. (1957-09-01). "The Tonofibrils of the Human Epidermis1". Journal of Investigative Dermatology. 29 (5): 327–338. doi:10.1038/jid.1957.108. ISSN 0022-202X. PMID 13502588.