Characterization of the insulin-like growth factor axis in the human thymus.
The components of the insulin-like growth factor (IGF) axis have been investigated in the normal human thymus. Using ribonuclease protection assays (RPA), IGF-II transcripts were detected in the normal human thymus. By reverse transcriptase polymerase chain reaction (RT-PCR) analyses, promoters P3 and P4 were found to be active in the transcription of IGF2 gene within human thymic epithelial cells (TEC). No IGF-II mRNA could be detected in human lymphoid Jurkat T cells with 30 cycles of RT-PCR. By Northern blot analyses, IGFBP-2 to -6 (but not IGFBP-1) were found to be expressed in TEC with a predominance of IGFBP-4. Interestingly, Jurkat T cells only express IGFBP-2 but at high levels. The type 1 IGF receptor was detected in Jurkat T cells but not in human TEC. The identification of the components of the IGF axis within separate compartments of the human thymus adds further evidence for a role of this axis in the control of T-cell development. The precise influence of thymic IGF axis upon T-cell differentiation and immunological self-tolerance however needs to be further investigated.
Kecha
O
O
Institute of Pathology CHU-B23, Laboratory of Molecular Oncology, University of Liège, Liège, Belgium. s903012@student.ulg.ac.be
Martens
H
H
Franchimont
N
N
Achour
I
I
Hazée-Hagelstein
M T
MT
Charlet-Renard
C
C
Geenen
V
V
Winkler
R
R
D015139:Blotting, Southern; D002675:Child, Preschool; D006801:Humans; D017403:In Situ Hybridization; D007223:Infant; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D019169:Jurkat Cells / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000378:metabolism; D013002:Somatomedins / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000502:physiology*
D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; D012313:RNA; D007335:Insulin-Like Growth Factor II; D012260:Ribonucleases