Lahmers Kevin K, Norimine Junzo, Abrahamsen Mitchell S, Palmer Guy H, Brown Wendy C
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA.
J Leukoc Biol. 2005 Feb;77(2):199-208. doi: 10.1189/jlb.0804482. Epub 2004 Nov 2.
Major surface protein 2 (MSP2) of the bovine rickettsial pathogen Anaplasma marginale is an abundant, serologically immunodominant outer membrane protein. Immunodominance partially results from numerous CD4+ T cell epitopes in highly conserved amino and carboxy regions and the central hypervariable region of MSP2. However, in long-term cultures of lymphocytes stimulated with A. marginale, workshop cluster 1 (WC1)+ gammadelta T cells and CD4+ alphabeta T cells proliferated, leading to a predominance of gammadelta T cells. As gammadelta T cells proliferate in A. marginale-stimulated lymphocyte cultures, this study hypothesized that gammadelta T cells respond to the abundant, immunodominant MSP2. To test this hypothesis, gammadelta T cell clones were isolated from MSP2 vaccinates and assessed for antigen-specific proliferation and interferon-gamma secretion. Seven WC1+ gammadelta T cell clones responded to A. marginale and MSP2, and three of these proliferated to overlapping peptides from the conserved carboxy region. The gammadelta T cell response was not major histocompatibility complex-restricted, although it required antigen-presenting cells and was blocked by addition of antibody specific for the T cell receptor (TCR). Sequence analysis of TCR-gamma and -delta chains of peripheral blood lymphocytes identified two novel TCR-gamma chain constant (Cgamma) regions. It is important that all seven MSP2-specific gammadelta T cell clones used the same one of these novel Cgamma regions. The TCR complementarity-determining region 3 was less conserved than those of MSP2-specific CD4+ alphabeta T cell clones. Together, these data indicate that WC1+ gammadelta T cells recognize A. marginale MSP2 through the TCR and contribute to the immunodominant response to this protein.
牛立克次氏体病原体边缘无形体的主要表面蛋白2（MSP2）是一种丰富的、血清学上免疫显性的外膜蛋白。免疫显性部分源于MSP2高度保守的氨基和羧基区域以及中央高变区中的众多CD4 + T细胞表位。然而，在用边缘无形体刺激的淋巴细胞长期培养物中，车间簇1（WC1）+ γδ T细胞和CD4 + αβ T细胞增殖，导致γδ T细胞占优势。由于γδ T细胞在边缘无形体刺激的淋巴细胞培养物中增殖，本研究假设γδ T细胞对丰富的、免疫显性的MSP2有反应。为了验证这一假设，从接种MSP2的动物中分离出γδ T细胞克隆，并评估其抗原特异性增殖和γ干扰素分泌情况。七个WC1 + γδ T细胞克隆对边缘无形体和MSP2有反应，其中三个对来自保守羧基区域的重叠肽增殖。γδ T细胞反应不受主要组织相容性复合体限制，尽管它需要抗原呈递细胞，并且通过添加针对T细胞受体（TCR）的特异性抗体而被阻断。外周血淋巴细胞TCR-γ和-δ链的序列分析鉴定出两个新的TCR-γ链恒定（Cγ）区域。重要的是，所有七个MSP2特异性γδ T细胞克隆都使用了这些新Cγ区域中的同一个。TCR互补决定区3比MSP2特异性CD4 + αβ T细胞克隆的保守性更低。总之，这些数据表明WC1 + γδ T细胞通过TCR识别边缘无形体MSP2，并对该蛋白的免疫显性反应有贡献。
