Major histocompatibility complex class II association and induction of T cell responses by carbohydrates and glycopeptides.
Major histocompatibility complex class II association and induction of T cell responses by carbohydrates and glycopeptides.
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主要组织相容性复合物 II 类关联以及碳水化合物和糖肽诱导 T 细胞反应。
DOI：
10.1007/bf00201108
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Grey,HM
中科院分区：
文献类型：
--
作者：
Ishioka,GY;Lamont,AG;Thomson,D;Bulbow,N;Gaeta,FC;Sette,A;Grey,HM
结论在接下来的研究中，我们研究了不能产生针对碳水化合物抗原的T细胞免疫是否是碳水化合物不能与II类MHC分子形成复合物的结果，或者是免疫库中碳水化合物特异性T细胞缺乏的结果。这些可能性首先通过测定纯碳水化合物分子的MHC结合能力，其次通过评估是否可以针对具有与II类MHC限制性元件相互作用的能力的糖基化T细胞肽表位诱导碳水化合物特异性T细胞来检验。测试了一组合成和天然寡糖和糖脂结合IAd II类分子的能力。在分析的26种碳水化合物中，没有发现与IAD显着结合。虽然只有少数有限的结构异质性的碳水化合物分子进行了测试MHC的结合，看来，纯碳水化合物和糖脂不具有必要的适当的结构，以结合II类MHC molecular. As碳水化合物可能固有地缺乏MHC结合活性，我们接下来解决是否糖肽具有MHC结合活性可以诱导T细胞特异性的碳水化合物结构。合成了一系列具有良好特征的T细胞决定簇（鸡OVA 323-339肽）的类似物，其中N-乙酰基葡糖胺取代置于肽分子内。用糖基化的OVA肽进行的实验表明三种一般类型的应答。在第一种类型的反应中，加入GlcNAc-天冬酰胺的OVA肽完全破坏了MHC的结合能力，因此，这些肽在体内对T细胞是非免疫原性的。在A329、A330和A332处取代的肽都显示出这种模式。位置332处的Ala先前显示参与与MHC分子的相互作用;因此，具有庞大侧链基团的残基预期会干扰结合[22]。对于位置A329和A330，MHC结合的缺乏不能由GlcNAc侧链的庞大性来解释。对于这些肽，糖分子可能对肽结构造成了不确定的干扰，从而完全消除了MHC结合。在第二类反应中，GlcNAc-Asn的取代似乎具有良好的耐受性，因为此类类似物结合II类MHC分子并在体内引发T细胞。当将N-乙酰葡糖胺置于MHC接触位点（例如，在V327处）或在核心区之外足够远的位置处，在那里它不太可能影响MHC结合并与T细胞受体相互作用（例如，在位置Q325和N335处）。针对这组肽产生的细胞对非糖基化类似物具有高度交叉反应性，进一步强调了T细胞识别不针对碳水化合物残基。当GlcNAc-Asn被置于肽的核心区域附近或内部的位置A326、H328和H331时，观察到第三种类型的反应。这些肽的MHC结合能力基本上但不完全减少，糖基化后存在的结合残留量仍然足以使糖肽在H-2d小鼠中具有免疫原性。有趣的是，针对这些糖肽的T细胞未能与其各自的Asn取代的类似物交叉反应，这表明肽上的碳水化合物结构是T淋巴细胞识别的抗原决定簇的组成部分。
ConclusionsIn the following study we have investigated whether the inability to generate T cell immunity against carbohydrate antigens is the result of a failure of carbohydrates to form a complex with class II MHC molecules or a deficiency of carbohydratespecific T cells in the immune repertoire. These possibilities were examined by, first, determining the MHC binding capacity of pure carbohydrate molecules and, second, by assessing whether carbohydrate-specific T cells could be induced against a glycosylated T cell peptide epitope which had the capacity to interact with class II MHC restriction elements.In the first set of experiments, a group of synthetic and natural oligosaccharides and glycolipids were tested for their ability to bind IAdclass II molecules. Of the 26 carbohydrates analyzed, none were found to bind significantly to IAd. Although only a small number of carbohydrate molecules of limited structural heterogeneity was tested for MHC binding, it appears that pure carbohydrates and glycolipids do not have the appropriate structures necessary to bind class II MHC molecules.Since carbohydrates may inherently lack MHC binding activity, we next addressed whether glycopeptides having MHC binding activity could induce T cells specific for the carbohydrate structure. A series of analogs of a well-characterized T cell determinant, the chicken OVA 323–339 peptide, was synthesized with aN-acetyl glucosamine substitution placed within the peptide molecule. Experiments performed with the glycosylated OVA peptides indicated three general types of response. In the first type of response, the addition of GlcNAc-Asn to the OVA peptide completely destroyed MHC binding capacity and, as a consequence, these peptides were nonimmunogenic for T cells in vivo. Peptides substituted at A329, A330, and A332 all showed this pattern. The Ala in position 332 was previously shown to be involved in interacting with the MHC molecule; thus, residues with bulky side chain groups would be expected to interfere with binding [22]. For positions A329 and A330, the lack of MHC binding could not be explained by the bulkiness of the GlcNAc side chain. For these peptides, the sugar molecule may have caused an undefined perturbation in peptide structure which completely ablated MHC binding.In the second category of response, substitution of GlcNAc-Asn appeared to be well tolerated since such analogs bound class II MHC molecules and primed T cells in vivo. This pattern was observed when theN-acetyl glucosamine was placed at an MHC contact site (e.g., at V327) or at a location sufficiently outside the core region where it was less likely to affect MHC binding and interact with the T cell receptor (e.g., at positions Q325 and N335). The cells generated against this set of peptides were highly cross-reactive for the nonglycosylated analog, further emphasizing that T cell recognition was not directed at the carbohydrate residue.A third type of response was observed when GlcNAc-Asn was placed near or within the core region of the peptide in positions A326, H328, and H331. The MHC binding capacity of these peptides was substantially but not completely diminished and the residual amount of binding present after glycosylation was still sufficient for the glycopeptide to be immunogenic in H-2dmice. Interestingly, T cells raised against these glycopeptides failed to cross-react with its respective Asn-substituted analog, suggesting that the carbohydrate structure on the peptide was an integral part of the antigenic determinant recognized by the T lymphocyte.Collectively, results obtained in the present study indicate …