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T-cell apoptosis and differential human leucocyte antigen class II expression in human thymus
1Transplantation Biology Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital, London, UK.
Immunology
|February 26, 2000
Summary
Human thymus exhibits unique human leucocyte antigen (HLA) class II expression, particularly in Hassall's corpuscles (HC), which are sites of thymocyte apoptosis. This suggests HC play a role in T-cell selection and tolerization.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Human leucocyte antigen (HLA) expression patterns in the thymus are not fully understood.
- Major histocompatibility complex (MHC) expression in specific thymic sites influences T-cell receptor (TCR) repertoire selection.
- Previous studies noted restricted MHC expression in the thymus.
Purpose of the Study:
- To analyze human thymic HLA class II expression.
- To correlate HLA expression patterns with thymocyte apoptosis sites.
- To investigate the role of Hassall's corpuscles (HC) in thymic selection.
Main Methods:
- Immunohistochemical analysis of human thymus.
- Detection of HLA class II molecules (HLA-DR, -DQ, -DP, -DM, -DO).
- Identification of apoptotic thymocytes and their location within the thymus.
Main Results:
- Human thymus strongly expresses HLA-DQ and HLA-DR.
- Hassall's corpuscles (HC) show unique HLA class II expression: negative for HLA-DR/DP, positive for HLA-DQ/DM.
- Apoptotic thymocytes are found in HC, including CD4+SP, CD8+SP, and DP cells.
Conclusions:
- Hassall's corpuscles (HC) exhibit unusual HLA class II expression and are the sole medullary site of thymocyte apoptosis.
- HC may serve as a crucial site for T-cell activation/tolerization via apoptotic cell peptide processing.
- Differential HLA transcriptional control in HC might influence specific T-cell subpopulations.