Smith C I, Baskin B, Christensson B, Sideras P, Hammarström L, Islam K B
Center for BioTechnology, Karolinska Institute at NOVUM, Huddinge, Sweden.
Immunodeficiency. 1993;4(1-4):231-5.
Immunoglobulin isotype switching is preceded by transcription of exons located 5' of the immunoglobulin switch regions. These exons are referred to as 'I-exons' and transcription of these regions is believed to be an essential step in switch recombination. Such mRNA species lack a variable portion and are denoted 'germline' transcripts. We have previously identified I-regions in man and we have now investigated the in vivo expression of human germline transcripts. Germline alpha transcripts (containing an I alpha exon) were expressed in various lymphoid organs, including peripheral blood mononuclear cells. Decreased levels of germline transcripts were found in immunoglobulin deficiency diseases. These findings are compatible with an in vivo role of germline transcription in isotype switching and may contribute to the understanding of mechanisms underlying deficiency diseases.
免疫球蛋白同种型转换之前，位于免疫球蛋白转换区5'端的外显子会进行转录。这些外显子被称为“I-外显子”，这些区域的转录被认为是转换重组中的关键步骤。此类mRNA缺乏可变区，被称为“种系”转录本。我们之前已在人类中鉴定出I区，现在我们研究了人类种系转录本的体内表达情况。种系α转录本（包含一个Iα外显子）在包括外周血单核细胞在内的多种淋巴器官中表达。在免疫球蛋白缺乏疾病中发现种系转录本水平降低。这些发现与种系转录在同种型转换中的体内作用相符，可能有助于理解缺乏疾病的潜在机制。
