Is There an Interspecific Diversity of the Thymic Microenvironment?

Thymic epithelial cells (TEC) heterogeneity suggests the existence of functional subsets.Anti-cytokeratin (Anti-CK) monoclonal antibodies (MAb), markers of epithelialdifferentiation, have been used to detect TEC subsets in rodents and humans. TheseMAb revealed a different topography of CK-defined TEC subsets in mice and humans,leading us to carry out a comparative study of mammalian thymuses. Our studyshowed that the distribution pattern of cytokeratins in the thymic epithelium is complexand unique, with coexpression of CK typical of simple and stratified epithelia.Moreover, we demonstrated an interspecific diversity of CK expression within thethymic lobules. Interestingly, such diversity was not a general phenomenon for theexpression of any thymic microenvironmental proteins, because the location ofextracellular matrix components was essentially similar in the mammalian speciesstudied.