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Updated: Aug 8, 2026
Isolation, Identification, and Purification of Murine Thymic Epithelial Cells
Published on: August 8, 2014
Cytokeratin expression in normal human thymus at different ages
A Masunaga1, I Sugawara, H Nakamura
1Department of Laboratory Medicine, University of Tokyo, Japan. atsuko@ims.u-tokyo.ac.jp
Insights
Thymic epithelial cell phenotypes were analyzed for cytokeratin (CK) expression during development and early involution. Changes in CK expression indicate a dynamic thymic microenvironment even in normal conditions.
Area of Science:
- Immunology
- Cell Biology
- Histology
Background:
- Thymic epithelial cells (TECs) are crucial for T-cell development.
- Understanding TEC phenotype changes is vital for immune system research.
- Cytokeratin (CK) expression patterns can reflect cellular differentiation and function.
Purpose of the Study:
- To investigate changes in TEC phenotypes during thymic growth and early involution.
- To analyze the expression patterns of specific cytokeratins (CK4, CK8, CK13, CK18, CK19) in TECs.
- To determine if TEC phenotypes vary with age and thymic involution stages.
Main Methods:
- Immunohistochemistry was used to examine TECs from neonatal, infantile, and adult thymus specimens.
- Five monoclonal antibodies specific for CK4, CK8, CK13, CK18, and CK19 were employed.
- Light and electron microscopy were utilized to analyze CK expression and cellular structures.
Main Results:
- CK4, CK8, CK13, CK18, and CK19 were co-expressed in the cortex, medulla, and subcapsular areas of neonatal and infantile thymuses.
- CK4 expression was observed in adult thymus, while CK4, CK13, and CK18 immunoreactivity decreased in the subcapsular area during early involution.
- Overlapping expression of CK8 and CK19 suggested complex formation within TEC cytoplasm, and variable CK18 patterns indicated a changeable thymic microenvironment.
Conclusions:
- TEC phenotypes, as indicated by CK expression, undergo changes during thymic development and early involution.
- The observed alterations in CK expression highlight the dynamic nature of the thymic microenvironment.
- Specific CK expression patterns may serve as biomarkers for thymic epithelial cell status and function.
Abstract:
Subsets of thymic epithelial cells were examined immunohistochemically to determine whether or not their phenotypes change during thymic growth and at early involution in terms of cytokeratin (CK) expression. Five monoclonal antibodies specific for CK4, CK8, CK13, CK18 and CK19 were used and applied to 16 neonatal, three infantile and one adult thymus specimen, which had been obtained at autopsy, that were normal macroscopically and microscopically. CK4, CK8, CK13, CK18 and CK19 were expressed simultaneously in the cortex, medulla and subcapsular area with the exception of CK4, which showed expression on the adult thymus. Light and electron microscopy showed that CK8 and CK19 expression was overlapped. Thus, it was thought that CK8 and CK19 formed complexes in the cytoplasm of thymic epithelial cells. The immunoreactivity to CK4, CK13 and CK18 were attenuated or disappeared in the subcapsular area during the early involution stage. Interestingly, two patterns of CK18 expression were observed in the neonatal and infantile thymus tissues, which indicated that the thymic microenvironment was changeable even under normal conditions.
