Cluster of differentiation 4 (CD4) is the accessory protein non-covalently bounded to T cell receptor (TCR) that recognize an invariant region of MHC class II on antigen presenting cell (APC). Its cytoplasmic tail, physically associated with a protein tyrosine kinase, is important in the activation of helper/inducer T (TH) lymphocytes. The anti-bovine CD4 monoclonal antibody (mAb) CC8 is a clone usefully used in flow cytometry assay in the last 20 years and no anomalous labelling has been described in previous reports. The aim of this study was to investigate the lack and reduced binding of clone CC8 to TH lymphocytes in three different breeds of dairy cattle: Italian Friesian (FRI), Pezzata Rossa Friulana (PRI) and their crossbreed (MET). Two unexpected flow cytometric phenotypes were found: CC8+ (reduced labelling) in 25%, 35% and 15% of the animals in the three breeds respectively, and CC8- (complete lack of labelling) in 15% of PRI cows. The complete sequencing of CD4 coding region (CDS) has allowed to identify two new missense mutations in the exon 5: Q306H and K310 N associated with the two phenotypes. A further new synonymous mutation (g.103634725 G > A) was found in exon 6. Further studies are needed to understand the effects of the news mutations, but these results demonstrate that flow cytometry is a powerful tool to discover polymorphic determinants of antigens involved in the immune responses.

中文翻译：

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牛CD4抗原的一个新的多态性表位通过流式细胞术证明。

分化簇4（CD4）是与T细胞受体（TCR）非共价结合的辅助蛋白，可识别抗原呈递细胞（APC）上II类MHC的恒定区。它的细胞质尾巴与蛋白酪氨酸激酶物理相关，在辅助/诱导性T（TH）淋巴细胞的激活中很重要。抗牛CD4单克隆抗体（mAb）CC8是最近20年用于流式细胞术分析的有用克隆，以前的报道中没有描述异常标记。这项研究的目的是研究克隆的CC8与TH淋巴细胞在三种不同品种的奶牛中的缺乏和结合减少：意大利Friesian（FRI），Pezzata Rossa Friulana（PRI）及其杂交（MET）。发现了两种意想不到的流式细胞仪表型：CC8 +（标记减少）占25％，这三个品种中分别有35％和15％的动物，以及15％的PRI奶牛的CC8-（完全缺乏标签）。CD4编码区（CDS）的完整测序已允许在外显子5中鉴定出两个新的错义突变：与这两个表型相关的Q306H和K310N。在外显子6中发现了另一个新的同义词突变（g.103634725 G> A）。需要进一步的研究以了解新闻突变的影响，但这些结果表明流式细胞仪是发现涉及抗原的多态决定簇的有力工具。在免疫反应中。