An in vitro model of T cell receptor revision in mature human CD8⁺ T cells

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• 作者：Erica Lantelme ; Luca Orl ; o ; Paola Porcedda ; Valentina Turinetto ; Mario De Marchi ; Antonio Amoroso ; Stefania Mantovani ; Claudia Giachino
• 关键词：Human ; T cells ; TCR revision ; RAG-1 ; RAG-2 ; IL7 ; TCR/CD3 down-regulation
• 刊名：Molecular Immunology
• 出版年：2008
• 期刊代码：112_01615890
• 类别：bio
• 出版时间：January 2008
• 卷：45
• 期：2
• 页码：328-337
• 文件大小：780 K

摘要

V(D)J recombination is a mechanism peculiar to the somatic rearrangement of antigen receptor genes. It requires both expression of the RAG-1 and RAG-2 recombinases and accessibility of the substrate to its recombinase and post-cleavage/DNA repair stage. TCR revision is a genetic correction mechanism that changes T cell specificity by re-activating V(D)J recombination in peripheral T cells. This process is now well described in both normal or pathological murine and human settings. Many of its features, such as the question of whether it occurs in truly mature T cells, remain to be elucidated. Its occurrence in human CD8⁺ T cells is also an open question.

We have therefore established an in vitro model of TCR revision in mature human CD8⁺ T cells to determine whether down-regulation of the TCR/CD3 complex from the cell surface in the presence of IL7 as a factor favouring chromatin remodelling initiates a TCR revision pathway. Only mature CD8⁺ T cells carrying already-formed antigen receptors were used. CD8⁺ T cells treated with anti-CD3 and IL7 showed rearrangement intermediates and expressed new Vβ-chains on their surface. Investigation of the molecular pathway thus induced disclosed up-regulation of the RAG-2 transcript, but absence of the ‘canonical’ RAG-1 mRNA. A surprising finding was the demonstration of alternative splice forms of this mRNA, already expressed in untreated CD8⁺ T cells, encoding for the full-length RAG-1 protein, which was increased three-fold in the treated cells.

All the V(D)J requirements were thus fulfilled when mature human CD8⁺ T cells were stimulated with anti-CD3 and IL7. Induction of TCR revision in vitro in mature T cells is an easily controllable system that could be employed in further studies to elucidate the molecular pathways involved in secondary V(D)J rearrangements in peripheral cells.