Happ M P, Palmer E
Department of Pediatrics, National Jewish Center for Immunology and Respiratory, Denver, CO 80206.
Eur J Immunol. 1989 Jul;19(7):1317-25. doi: 10.1002/eji.1830190725.
We have examined the frequency of expression of individual alpha and beta chain V gene families in a population of immature T cells that has not been selected or tolerized. To accomplish this, we generated 519 T cell hybridomas from freshly isolated thymocytes of newborn C57BL/10 mice and subjected RNA from these hybrids to hybridization analysis with 11 V alpha, 16 V beta, C gamma and C delta probes. Comparison of the expressed repertoire of V beta gene segments in this newborn thymocyte population with similar data previously generated from adult peripheral T cells (Bill et al., Proc. Natl. Acad. Sci. USA 1988. 85: 9184.) revealed two V beta genes, V beta 12 and V beta 15, whose expression is decreased in the periphery possibly due to the effects of tolerance. An additional V beta gene segment (V beta 10) and a V beta gene family (V beta 5.1, V beta 5.2) were expressed more frequently in the mature, peripheral population than in the newborn thymus. These findings may represent two instances of positive selection of T cells. Furthermore, unlike VH gene segments, D beta-proximal V beta genes are not overrepresented on this collection of immature thymocyte hybridomas. A similar analysis of V alpha gene family expression was hampered by the fact that V alpha gene segments were expressed in only 15% of newborn thymocyte hybridomas (compared to 58% of adult hybridomas). An unexpectedly large fraction (57%) of those newborn hybrids expressing a V alpha gene segment was also found to express C delta mRNA and further examination revealed that several V alpha gene probes were actually detecting delta chain mRNA. The most notable of these was the V alpha 7 gene family, which accounted for approximately one-third of the expressed V alpha genes but was expressed exclusively as part of a delta chain mRNA. We found no examples of hybridomas co-expressing both full-length alpha and delta chain mRNA, despite significant numbers of hybridomas co-expressing full-length beta and gamma chain transcripts. This observation suggests that a large number of mature alpha/beta T cells may have proceeded through development without having gone through a stage where a delta chain message is expressed, thereby precluding their development into gamma/delta cells.
我们检测了一群未经选择或耐受的未成熟T细胞中单个α和β链V基因家族的表达频率。为实现这一目的，我们从新生C57BL/10小鼠新鲜分离的胸腺细胞中产生了519个T细胞杂交瘤，并使用11个Vα、16个Vβ、Cγ和Cδ探针，对这些杂交瘤的RNA进行杂交分析。将该新生胸腺细胞群体中Vβ基因片段的表达库与先前从成年外周T细胞获得的类似数据（Bill等人，《美国国家科学院院刊》1988年。85: 9184.）进行比较，发现两个Vβ基因，Vβ12和Vβ15，其在外周的表达降低，可能是由于耐受的影响。另外一个Vβ基因片段（Vβ10）和一个Vβ基因家族（Vβ5.1、Vβ5.2）在成熟的外周群体中比在新生胸腺中表达更频繁。这些发现可能代表了T细胞阳性选择的两种情况。此外，与VH基因片段不同，Dβ近端Vβ基因在这群未成熟胸腺细胞杂交瘤中并未过度表达。对Vα基因家族表达的类似分析受到以下事实的阻碍：Vα基因片段仅在15%的新生胸腺细胞杂交瘤中表达（相比之下，成年杂交瘤的表达率为58%）。还发现，那些表达Vα基因片段的新生杂交瘤中有出乎意料的很大一部分（57%）也表达Cδ mRNA，进一步检查发现，几个Vα基因探针实际上检测到的是δ链mRNA。其中最显著的是Vα7基因家族，它占所表达Vα基因的约三分之一，但仅作为δ链mRNA的一部分表达。尽管有大量杂交瘤共表达全长β和γ链转录本，但我们未发现共表达全长α和δ链mRNA的杂交瘤实例。这一观察结果表明，大量成熟的α/β T细胞可能在发育过程中未经历表达δ链信息的阶段，从而排除了它们发育为γ/δ细胞的可能性。
