Background: The immune system is able to recognize substances that originate from inside or outside the body and are potentially harmful. Foreign substances that bind to immune system components exhibit antigenicity and are defined as antigens. The antigens exhibiting immunogenicity can induce innate or adaptive immune responses and give rise to humoral or cell-mediated immunity. The antigens exhibiting mitogenicity can cross-link cell membrane receptors on B and T lymphocytes leading to cell proliferation. All antigens vary greatly in physicochemical features such as biochemical nature, structural complexity, molecular size, foreignness, solubility, and so on. Objective:: Thus, this review aims to describe the molecular bases of protein-antigenicity and those molecular bases that lead to an immune response, lymphocyte proliferation, or unresponsiveness. Conclusion: The epitopes of an antigen are located in surface areas; they are about 880-3,300 Da in size. They are protein, carbohydrate, or lipid in nature. Soluble antigens are smaller than 1 nm and are endocytosed less efficiently than particulate antigens. The more the structural complexity of an antigen increases, the more the antigenicity increases due to the number and variety of epitopes. The smallest immunogens are about 4,000-10,000 Da in size. The more phylogenetically distant immunogens are from the immunogen-recipient, the more immunogenicity increases. Antigens that are immunogens can trigger an innate or adaptive immune response. The innate response is induced by antigens that are pathogen-associated molecular patterns. Exogenous antigens, T Dependent or T Independent, induce humoral immunogenicity. TD protein-antigens require two epitopes, one sequential and one conformational to induce antibodies, whereas, TI non-protein-antigens require only one conformational epitope to induce low-affinity antibodies. Endogenous protein antigens require only one sequential epitope to induce cell-mediated immunogenicity.

中文翻译：

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蛋白质抗原性的分子基础和免疫原性、无反应性和有丝分裂性的决定因素

背景：免疫系统能够识别来自体内或体外且具有潜在危害的物质。与免疫系统成分结合的外来物质表现出抗原性，被定义为抗原。表现出免疫原性的抗原可以诱导先天性或适应性免疫反应并产生体液或细胞介导的免疫。表现出有丝分裂活性的抗原可以交联 B 和 T 淋巴细胞上的细胞膜受体，导致细胞增殖。所有抗原在生化性质、结构复杂性、分子大小、异源性、溶解性等理化特征上都有很大差异。目的：因此，本综述旨在描述蛋白质抗原性的分子基础以及导致免疫反应、淋巴细胞增殖或无反应的分子基础。结论：抗原的表位位于表面区域；它们的大小约为 880-3,300 Da。它们本质上是蛋白质、碳水化合物或脂质。可溶性抗原小于 1 nm，内吞效率低于颗粒抗原。抗原的结构复杂性增加得越多，由于表位的数量和种类而导致的抗原性也增加得越多。最小的免疫原大小约为 4,000-10,000 Da。免疫原与免疫原受体的系统发育距离越远，免疫原性就越高。作为免疫原的抗原可以触发先天性或适应性免疫反应。先天反应是由病原体相关分子模式的抗原诱导的。外源抗原（T 依赖性或 T 独立性）诱导体液免疫原性。TD 蛋白质抗原需要两种表位（一种连续表位和一种构象表位）来诱导抗体，而 TI 非蛋白质抗原仅需要一种构象表位来诱导低亲和力抗体。内源性蛋白质抗原仅需要一个连续表位即可诱导细胞介导的免疫原性。