In this work, chicken HPAIV H5N1 epitope-specific TCRαβ (ch-TCRαβ) was isolated and its structure was determined. The Cα domain of ch-TCRαβ does not exhibit the typical structure of human TCRαβ, and the DE loop extends outward, resulting in close proximity between the Cα domain of ch-TCRαβ and CD3εδ/γ. The FG loop of the Cβ domain of ch-TCRαβ is shorter. The changes in the C domains of ch-TCRαβ and the difference in chicken CD3εδ/γ confirm that the complexes formed by TCRαβ and CD3εδ/γ differ from those in humans. In the chicken complex, a positively charged cleft is formed between the two CDR3 loops that might accommodate the acidic side chains of the chicken pMHC-I-bound HPAIV epitope intermediate portion oriented toward ch-TCRαβ. This is the first reported structure of chicken TCRαβ, and it provides a structural model of the ancestral TCR system in the immune synapses between T cells and antigen-presenting cells in lower vertebrates.

在这项工作中，分离了鸡HPAIV H5N1表位特异性TCRαβ（ch-TCRαβ），并确定了其结构。ch-TCRαβ的Cα结构域未表现出人TCRαβ的典型结构，DE环向外延伸，导致ch-TCRαβ的Cα结构域与CD3εδ/γ紧密接近。ch-TCRαβ的Cβ结构域的FG环较短。ch-TCRαβ的C结构域的变化以及鸡CD3εδ/γ的差异证实了TCRαβ和CD3εδ/γ形成的复合物与人的复合物不同。在鸡复合物中，两个CDR3环之间形成带正电荷的裂口，这两个环可容纳鸡pMHC-1结合的HPAIV表位中间部分的酸性侧链，其朝向ch-TCRαβ。这是鸡TCRαβ的第一个报道结构，