Aire and Foxp3 expression in a particular microenvironment for T cell differentiation.
OBJECTIVE
The thymus is the primary lymphoid organ responsible for T cell development and the establishment of central self-tolerance. Among thymic epithelial cells, thymic nurse cells (TNC) interact closely with immature thymocytes and constitute a special microenvironment for T cell differentiation and selection. In addition, TNC express neuroendocrine self-antigens such as oxytocin and insulin-like growth factor-2, whose intrathymic transcription is regulated by the autoimmune regulator gene/protein (Aire). Both effector and natural regulatory T cell (nTreg) lineages develop in the thymus, but the mechanisms leading to nTreg selection in the thymus are still unclear. Foxp3 is the most specific nTreg marker that is required for nTreg functional activity, but not for engagement into the Treg lineage. Aire has been suggested to be a potential factor implicated in this role. The objective of this study was to characterize Aire and Foxp3 expression in TNC/thymocyte complexes.


METHODS
Aire and Foxp3 expression was investigated by RT-qPCR in TNC/thymocyte complexes isolated by enzymatic digestion and sedimentation. Aire and Foxp3 proteins were located by confocal microscopy and specific immunocytochemistry.


RESULTS
Both Aire and Foxp3 transcripts were detected in TNC/thymocyte complexes. Foxp3 was detected in the nucleus of thymocytes internalized into TNC. Aire was located mainly in TNC cytoplasm and, although to a lower degree, in the nucleus of some TNC-associated thymocytes.


CONCLUSIONS
Aire and Foxp3 are present in the particular TNC microenvironment which has previously been shown to support thymic selection. The differential localization of these two markers suggests a role for TNC in nTreg development.
Hansenne
Isabelle
I
Center of Immunology, Institute of Pathology, Liege-Sart Tilman, Belgium.
Louis
Céline
C
Martens
Henri
H
Dorban
Gauthier
G
Charlet-Renard
Chantal
C
Peterson
Pärt
P
Geenen
Vincent
V
D000818:Animals; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D019070:Cell Lineage / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D007111:Immunity, Cellular / Q000502:physiology; D007150:Immunohistochemistry; D038041:Lymphopoiesis / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D013347:Subcellular Fractions; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development / Q000276:immunology*; D014157:Transcription Factors / Q000378:metabolism*; D000096927:AIRE Protein
D015415:Biomarkers; D051858:Forkhead Transcription Factors; D014157:Transcription Factors; D000096927:AIRE Protein; C498833:Foxp3 protein, mouse