IN-VITRO AND IN-SITU CHARACTERIZATION OF FISH THYMIC NURSE CELLS

We present an enzyme- and immuno-cytochemical, and ultrastructural cha racterization of trout thymic nurse cells (TNCs). Our data suggest tha t isolated trout thymic multicellular complexes are epithelial cells w ith acidic compartments that may be involved in the processing of anti gens and in the generation of the MHC-II proteins that these cell expr ess, and also that isolated TNCs are the in vitro equivalent of the pa le and intermediate electron-lucent epithelial cells located in the in ner zone of the trout thymus, constituting indirect evidence of the ph ylogenetical relationships of the inner zone of the teleost thymus wit h the thymic cortex of higher vertebrates.