CD3 is an essential component of the TCR-CD3 complex which plays a key role in adaptive immunity. Non-mammalian CD3 complex consists of CD3γ/δ, CD3ε and CD3ζ subunits. In this study, homologues of CD3γ/δ and CD3ε (termed CiCD3γ/δ and CiCD3ε) have been identified in grass carp (Ctenopharyngodon idella). Like their counterparts from other vertebrates, the CiCD3γ/δ and CiCD3ε are clustered in the same locus in the genome and encodes proteins which are structurally conserved, comprising a signal peptide, an extracellular domain, a transmembrane domain and a cytoplasmic tail containing two ITAM motifs. Sequence analyses identified two novel conserved motifs in the cytoplasmic tail of CiCD3γ/δ and CiCD3ε, one is composed of an arginine and lysine motif (RK or RR) at the C terminus of CiCD3γ/δ and a proline rich domain (PxxPxP/Q) located at the N terminus of ITAM motifs of CiCD3ε. Both genes were highly expressed at the mRNA level in spleen and gills of healthy fish and could be modulated by infection of Flavobacterium columnare and grass carp reovirus. A monoclonal antibody against the CiCD3γ/δ (GC38T) was produced and showed good reactivity with the native molecule in Western blotting and flow cytometry. The CiCD3γ/δ⁺ cells were analysed in the primary leucocytes, accounting for 5.5% of lymphocytes isolated from spleen, 4.5% from head kidney and 2.8% from peripheral blood. The CiCD3γ/δ⁺ cells were localized in the gills and head kidney by fluorescent confocal microscopy.

CD3 是 TCR-CD3 复合物的重要组成部分，在适应性免疫中起关键作用。非哺乳动物 CD3 复合物由 CD3γ/δ、CD3ε 和 CD3ζ 亚基组成。在本研究中，已在草鱼 ( Ctenopharyngodon idella ) 中鉴定出CD3γ/δ 和 CD3ε 的同源物（称为Ci CD3γ/δ 和Ci CD3ε ）。与其他脊椎动物的对应物一样，Ci CD3γ/δ 和Ci CD3ε 聚集在基因组中的同一位点并编码结构上保守的蛋白质，包括信号肽、细胞外结构域、跨膜结构域和含有两个ITAM 图案。序列分析确定了Ci的细胞质尾部中的两个新的保守基序CD3γ/δ 和Ci CD3ε，一个由Ci CD3γ/δ 的 C 末端的精氨酸和赖氨酸基序（RK 或 RR）和位于Ci的 ITAM 基序 N 末端的富含脯氨酸的结构域（PxxPxP/Q）组成CD3ε。这两个基因在健康鱼的脾脏和鳃中均在mRNA水平上高表达，并且可以受到柱状黄杆菌和草鱼呼肠孤病毒感染的调节。产生了针对Ci CD3γ/δ (GC38T)的单克隆抗体，并在蛋白质印迹和流式细胞术中显示出与天然分子的良好反应性。Ci CD3γ / δ ⁺在原代白细胞中分析细胞，占从脾脏分离的淋巴细胞的5.5%，从头肾分离的4.5%和从外周血分离的2.8%。Ci CD3γ/δ ⁺细胞通过荧光共聚焦显微镜定位在鳃和头肾中。