生殖中心内的亲和力成熟是如何通过反复的突变与选择实现的？
How does affinity maturation in the germinal centre proceed through repeated cycles of mutation and selection?
生殖中心分为暗区和亮区：B 细胞在暗区快速分裂，胞苷脱氨酶 AID 在免疫球蛋白可变区引入体细胞高频突变；随后迁移到亮区，与滤泡树突状细胞表面的抗原和滤泡辅助 T 细胞竞争性接触。抗原亲和力高的克隆能捕获更多抗原、获得更强的 T 细胞辅助信号（如 CD40L 与 IL-21），从而被选择性扩增并重新返回暗区继续突变。这种循环相当于活体内的达尔文式定向进化，最终产出高亲和力抗体和记忆细胞。
Germinal centres are split into a dark zone where B cells divide rapidly while the cytidine deaminase AID introduces somatic hypermutation into immunoglobulin variable regions, and a light zone where the cells compete for antigen displayed on follicular dendritic cells and for help from follicular helper T cells. Clones with higher affinity capture more antigen and receive stronger help signals such as CD40L and IL-21, so they are selectively expanded and cycle back to the dark zone for further mutation. This iterative loop is Darwinian selection inside the body, yielding high-affinity antibodies and memory cells.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Mesin L, Ersching J, Victora GD. Germinal center B cell dynamics. Immunity (2016) 45:471-482
Mesin L, Ersching J, Victora GD. Germinal center B cell dynamics. Immunity (2016) 45:471-482
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1016/j.immuni.2016.09.001
#生殖中心 #体细胞高频突变 #亲和力成熟 #滤泡辅助T细胞
MHC I 类与 II 类抗原提呈通路有何不同，交叉提呈为何对抗病毒和抗肿瘤免疫特别重要？
How do MHC class I and class II presentation pathways differ, and why is cross-presentation crucial for antiviral and antitumour immunity?
MHC I 类分子主要装载由蛋白酶体降解的胞内蛋白多肽，经 TAP 转运进内质网后提呈给 CD8 阳性细胞毒性 T 细胞；MHC II 类分子在内体溶酶体区室装载外源蛋白降解产物，提呈给 CD4 阳性辅助 T 细胞。交叉提呈是树突状细胞把摄取的外源抗原导入 MHC I 通路的能力，使免疫系统即使自身未被病毒感染或未表达肿瘤抗原，也能启动细胞毒性 T 细胞反应。这一机制是治疗性肿瘤疫苗和多数病毒疫苗诱导 CD8 反应的基础。
MHC class I molecules mainly load peptides from proteasome-degraded cytosolic proteins, delivered into the endoplasmic reticulum by TAP and shown to CD8-positive cytotoxic T cells, whereas class II molecules load fragments of exogenous proteins in endolysosomal compartments for CD4-positive helper T cells. Cross-presentation is the ability of dendritic cells to route internalized exogenous antigen into the class I pathway, so cytotoxic responses can be primed even when the presenting cell is not itself infected or transformed. This route underlies CD8 priming by most viral vaccines and by therapeutic cancer vaccines.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Janeway 等，《免疫生物学：健康与疾病中的免疫系统》（第9版，Garland Science，2016）
Janeway et al., Immunobiology: The Immune System in Health and Disease (9th ed., Garland Science, 2016)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL18294997W：Immunobiology : the im
#抗原提呈 #MHC #交叉提呈 #树突状细胞
为什么把 mRNA 中的尿苷替换为假尿苷等修饰核苷，能同时降低炎症并提高蛋白产量？
Why does replacing uridine with modified nucleosides such as pseudouridine both lower inflammation and raise protein output from mRNA?
未修饰的单链 RNA 会被 TLR7、TLR8 以及胞质内的 RIG-I、PKR 等先天免疫传感器识别为病原信号，触发干扰素反应并通过 PKR 磷酸化 eIF2α 抑制翻译起始。把尿苷替换为假尿苷或 N1-甲基假尿苷后，这些传感器的识别显著减弱，炎性细胞因子下降。同时因为翻译不再被 PKR 抑制、mRNA 稳定性提高，单位 mRNA 的蛋白产量可提升一个数量级，这是 mRNA 疫苗得以实用化的关键改造。
Unmodified single-stranded RNA is read as a danger signal by innate sensors including TLR7, TLR8, RIG-I and PKR, triggering interferon responses while PKR phosphorylates eIF2-alpha and shuts down translation initiation. Substituting uridine with pseudouridine or N1-methylpseudouridine sharply reduces sensor recognition and inflammatory cytokine release. Because translation is no longer blocked and transcript stability improves, protein yield per molecule can rise by roughly an order of magnitude, which was decisive for making mRNA vaccines practical.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Karikó K, Buckstein M, Ni H, Weissman D. Suppression of RNA recognition by Toll-like receptors. Immunity (2005) 23:165-175
Karikó K, Buckstein M, Ni H, Weissman D. Suppression of RNA recognition by Toll-like receptors. Immunity (2005) 23:165-175
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1016/j.immuni.2005.06.008
#核苷修饰 #假尿苷 #先天免疫传感器 #翻译效率
为什么麻疹疫苗只需接种一两次就能提供数十年保护,而流感疫苗却要每年更新配方?
Why does measles vaccination provide protection for decades after only one or two doses, while influenza vaccines need their formula updated every year?
麻疹病毒抗原高度保守,减毒活疫苗会在体内短暂复制,持续刺激生发中心,产生高亲和力记忆B细胞和能在骨髓中存活数十年的长寿命浆细胞。流感病毒的血凝素和神经氨酸酶则通过抗原漂移快速改变表面表位,原有免疫记忆难以识别新毒株。因此世界卫生组织每年依据全球监测数据预测下一流行季的优势毒株,重新确定疫苗组分。
Measles virus keeps a highly conserved antigen profile, and the live attenuated vaccine replicates briefly in the body, sustaining germinal-center reactions that generate high-affinity memory B cells and long-lived plasma cells able to persist in bone marrow for decades. Influenza virus instead alters its hemagglutinin and neuraminidase epitopes rapidly through antigenic drift, so established immune memory struggles to recognize new strains. The World Health Organization therefore redefines vaccine composition annually based on predictions drawn from global surveillance data.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Plotkin《Vaccines》(第7版,Elsevier)关于保护持久性与记忆B细胞的章节;世界卫生组织全球流感监测与应对体系(GISRS)年度疫苗组分建议
Plotkin's Vaccines (7th ed., Elsevier), chapters on durability of protection and memory B cells; WHO Global Influenza Surveillance and Response System (GISRS) annual composition recommendations
#疫苗技术 #免疫记忆
接种疫苗后，人体的免疫记忆主要由哪些细胞承担？
Which cell types carry the immune memory that a vaccine leaves behind?
记忆主要由三类细胞维持：长寿浆细胞驻留骨髓，持续分泌抗体形成第一道防线；记忆 B 细胞在再次遇到抗原时快速活化并可进一步亲和力成熟；记忆 T 细胞分为中央型、效应型和组织驻留型，分别负责再扩增和局部快速清除。抗体水平随时间下降不等于保护完全消失，因为记忆细胞仍可在再次感染时数天内重建高滴度反应。
Three populations dominate: long-lived plasma cells in the bone marrow that keep secreting antibody as a first barrier, memory B cells that reactivate and can undergo further affinity maturation on re-exposure, and memory T cells in central, effector and tissue-resident forms that re-expand or clear infection locally. A waning antibody titre therefore does not equal lost protection, because memory cells can rebuild a high-titre response within days of re-infection.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Sallusto F, Lanzavecchia A, Araki K, Ahmed R. From vaccines to memory and back. Immunity (2010) 33:451-463
Sallusto F, Lanzavecchia A, Araki K, Ahmed R. From vaccines to memory and back. Immunity (2010) 33:451-463
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1016/j.immuni.2010.10.008
#免疫记忆 #记忆B细胞 #长寿浆细胞 #记忆T细胞
mRNA 疫苗为什么必须用脂质纳米颗粒包裹后才能有效发挥作用？
Why do mRNA vaccines need to be packaged in lipid nanoparticles to work effectively?
裸露的 mRNA 带负电、分子量大，既会被血液和组织中的核酸酶迅速降解，也难以穿过同样带负电的细胞膜。脂质纳米颗粒由可电离脂质、辅助磷脂、胆固醇和聚乙二醇化脂质组成，把 mRNA 包裹起来避免降解，并通过内吞进入细胞后在酸性内体中释放 mRNA 到细胞质。脂质本身还有一定佐剂效应，可增强先天免疫的激活。
Naked mRNA is large and negatively charged, so it is rapidly degraded by extracellular ribonucleases and cannot cross the similarly charged plasma membrane. Lipid nanoparticles built from ionizable lipids, helper phospholipids, cholesterol and PEG-lipids shield the mRNA, enter cells by endocytosis, and release the cargo into the cytosol when the endosome acidifies. The lipid carrier also provides intrinsic adjuvant activity that strengthens innate immune activation.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Karikó、Weissman 等《RNA 修饰抑制 Toll 样受体激活》(Immunity, 2005)；Pardi、Weissman 等《mRNA 疫苗》(Nature Reviews Drug Discovery, 2018)；美国 CDC《新冠 mRNA 疫苗》
Karikó, Weissman et al., 'Suppression of RNA recognition by Toll-like receptors' (Immunity, 2005); Pardi, Hogan, Porter & Weissman, 'mRNA vaccines' (Nature Reviews Drug Discovery, 2018); US CDC, 'mRNA COVID-19 Vaccines'
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1016/j.immuni.2005.06.008：Suppression of
#mRNA 疫苗 #脂质纳米颗粒 #递送系统 #内体逃逸
群体免疫阈值是怎么估算的，为什么不同传染病的阈值差别很大？
How is the herd immunity threshold estimated, and why does it vary so much between diseases?
在简化的均匀混合模型中，群体免疫阈值约为 1 减去 1 除以基本再生数，即传染性越强、基本再生数越大，需要具备免疫力的人口比例越高。麻疹的基本再生数常在 12 到 18，阈值超过九成；流感等较低传染性疾病的阈值明显更低。实际阈值还受接种覆盖不均、人群接触结构、免疫保护随时间衰减以及病原体变异等因素影响，因此不能仅按公式机械套用。
In a simple homogeneous-mixing model the threshold is approximately one minus the reciprocal of the basic reproduction number, so the more transmissible the pathogen the larger the immune fraction required. Measles, with a basic reproduction number often quoted at 12 to 18, needs over 90 percent immunity, while less transmissible infections such as seasonal influenza need much less. Real thresholds also depend on uneven vaccine coverage, contact structure, waning protection and pathogen evolution, so the formula is only a first approximation.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Fine, Eames, Heymann,《"Herd Immunity": A Rough Guide》,Clinical Infectious Diseases,2011 (DOI: 10.1093/cid/cir007)
Fine, Eames, Heymann, '"Herd Immunity": A Rough Guide', Clinical Infectious Diseases, 2011, DOI: 10.1093/cid/cir007
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1093/cid/cir007
#群体免疫 #基本再生数 #疫苗覆盖率 #传染病模型
减毒活疫苗和 mRNA 疫苗在建立免疫记忆的方式上有什么关键差别?
What is the key difference between live-attenuated vaccines and mRNA vaccines in how they establish immune memory?
减毒活疫苗在体内进行有限复制,抗原在淋巴组织中持续表达数周,B 细胞、CD4 和 CD8 T 细胞都被广泛动员,形成的记忆接近自然感染。mRNA 疫苗并不复制,只由宿主细胞短暂翻译出抗原,记忆主要依赖树突细胞的交叉提呈和生发中心反应,通常需要加强针来扩充记忆细胞库。前者免疫广度更大但免疫缺陷者须慎用,后者组分简单、便于快速改造。
Live-attenuated vaccines replicate in a limited fashion, keeping antigen expressed in lymphoid tissue for weeks, so B cells along with CD4 and CD8 T cells are all broadly engaged and the resulting memory resembles natural infection. mRNA vaccines do not replicate; host cells translate the antigen only transiently, so memory rests mainly on dendritic-cell cross-presentation and germinal-center reactions, and boosters are usually needed to expand the memory pool. The former gives broader immunity but requires caution in immunocompromised recipients, while the latter is simple in composition and quick to redesign.
难度 进阶 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Plotkin《Vaccines》(第7版,Elsevier)关于保护持久性与记忆B细胞的章节;世界卫生组织全球流感监测与应对体系(GISRS)年度疫苗组分建议
Plotkin's Vaccines (7th ed., Elsevier), chapters on durability of protection and memory B cells; WHO Global Influenza Surveillance and Response System (GISRS) annual composition recommendations
#免疫记忆 #mRNA疫苗
先天免疫与适应性免疫在识别方式和反应速度上有什么根本差别？
How do innate and adaptive immunity differ in the way they recognize pathogens and in their response speed?
先天免疫依靠模式识别受体（如 Toll 样受体）识别病原体共有的保守分子模式，反应在数分钟到数小时内启动，但不产生记忆。适应性免疫依靠随机重排产生的 B 细胞受体和 T 细胞受体识别特定抗原表位，需要数天完成克隆扩增，却能形成长期免疫记忆。两者并非彼此独立，先天免疫的抗原提呈与共刺激信号决定了适应性反应的强度和类型。
Innate immunity relies on pattern-recognition receptors such as Toll-like receptors that detect conserved molecular patterns shared by microbes; it acts within minutes to hours but leaves no memory. Adaptive immunity uses somatically rearranged B-cell and T-cell receptors to recognize specific epitopes, requiring days for clonal expansion but generating durable memory. The two arms are coupled: antigen presentation and costimulatory signals from innate cells set the magnitude and flavour of the adaptive response.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Iwasaki A, Medzhitov R. Control of adaptive immunity by the innate immune system. Nature Immunology (2015) 16:343-353
Iwasaki A, Medzhitov R. Control of adaptive immunity by the innate immune system. Nature Immunology (2015) 16:343-353
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1038/ni.3123
#先天免疫 #适应性免疫 #模式识别受体 #免疫记忆
疫苗佐剂通过什么机制增强免疫应答？
By what mechanisms do vaccine adjuvants strengthen the immune response?
佐剂的作用可归为两类：一是延长抗原在注射部位的滞留并促进抗原被树突状细胞摄取和转运到淋巴结；二是直接激活先天免疫通路，提供细胞因子和共刺激环境。铝盐佐剂主要促进抗体反应并与炎症小体和局部损伤信号有关，而含 TLR4 激动剂单磷酰脂 A 与皂苷的 AS01 类佐剂能显著增强 T 细胞免疫，用于重组带状疱疹疫苗。佐剂选择因此决定了疫苗诱导的免疫类型，而不只是强度。
Adjuvants act in two broad ways: they prolong antigen retention at the injection site and promote uptake and transport of antigen by dendritic cells to lymph nodes, and they directly engage innate pathways to supply cytokine and costimulatory context. Aluminium salts mainly boost antibody responses and are linked to inflammasome activation and local damage signals, whereas AS01-type adjuvants combining the TLR4 agonist monophosphoryl lipid A with a saponin markedly enhance T-cell immunity, as used in the recombinant zoster vaccine. Adjuvant choice therefore shapes the quality of immunity, not merely its magnitude.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Reed, Orr, Fox,《Key roles of adjuvants in modern vaccines》,Nature Medicine,2013 (DOI: 10.1038/nm.3409)
Reed, Orr, Fox, 'Key roles of adjuvants in modern vaccines', Nature Medicine, 2013, DOI: 10.1038/nm.3409
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1038/nm.3409
#佐剂 #铝盐 #TLR激动剂 #抗体反应