Age-associated thymic atrophy is linked to a decline in IL-7 production.
Age-associated thymic atrophy results in a decline in T lymphocyte output and has been identified as one of the key events that precede inefficient functioning of the immune system in later life. Thymic atrophy is thought to result from a failure of the thymic microenvironment to support thymopoiesis in old age and recent evidence suggests that a decline in interleukin-7 (IL-7) expression may limit thymocyte development by restricting combinations of survival, proliferation and rearrangement of the TCRbeta chain. Using RT-PCR and the RNase protection assay, we show that the expression of IL-7 declines with age. Analysis of Connexin 43 expression, a component molecule of gap junctions, whose function is to connect epithelial cells, does not markedly decline with age. These observations suggest that a decline in IL-7 expression is not matched by a similar loss of epithelial cells. These results in conjunction with other studies lead us to speculate that IL-7 producing MHC class II positive TECs are being replaced by cells that do not have this capacity.
Andrew
Deborah
D
Department of Immunology, ICSM at Chelsea & Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK. d.andrew@ic.ac.uk
Aspinall
Richard
R
D000375:Aging / Q000235:genetics / Q000276:immunology*; D000818:Animals; D001284:Atrophy; D018031:Connexin 43 / Q000235:genetics; D012321:DNA-Directed RNA Polymerases; D015870:Gene Expression; D015851:Interleukin-7 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019089:Stem Cell Factor / Q000235:genetics; D013950:Thymus Gland / Q000276:immunology / Q000473:pathology*; D014764:Viral Proteins
D018031:Connexin 43; D015851:Interleukin-7; D019089:Stem Cell Factor; D014764:Viral Proteins; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases