SARS-CoV-2 infection of children leads to a mild illness and the immunological differences with adults are unclear. Here, we report SARS-CoV-2 specific T cell responses in infected adults and children and find that the acute and memory CD4⁺ T cell responses to structural SARS-CoV-2 proteins increase with age, whereas CD8⁺ T cell responses increase with time post-infection. Infected children have lower CD4⁺ and CD8⁺ T cell responses to SARS-CoV-2 structural and ORF1ab proteins when compared with infected adults, comparable T cell polyfunctionality and reduced CD4⁺ T cell effector memory. Compared with adults, children have lower levels of antibodies to β-coronaviruses, indicating differing baseline immunity. Total T follicular helper responses are increased, whilst monocyte numbers are reduced, indicating rapid adaptive co-ordination of the T and B cell responses and differing levels of inflammation. Therefore, reduced prior β-coronavirus immunity and reduced T cell activation in children might drive milder COVID-19 pathogenesis.

儿童感染 SARS-CoV-2 会导致轻微疾病，与成人的免疫学差异尚不清楚。在这里，我们报告了受感染的成人和儿童中的 SARS-CoV-2 特异性 T 细胞反应，并发现对结构 SARS-CoV-2 蛋白的急性和记忆 CD4 ^{+ T 细胞反应随着年龄的增长而增加，而 CD8 +} T 细胞反应随着年龄的增长而增加。感染后的时间。与受感染的成人相比，受感染的儿童对 SARS-CoV-2 结构蛋白和 ORF1ab 蛋白的CD4 ⁺和 CD8 ^{+ T 细胞反应较低，T 细胞多功能性相当，并且 CD4 +} T 细胞效应记忆降低。与成人相比，儿童的β冠状病毒抗体水平较低，表明基础免疫力不同。滤泡辅助 T 细胞总反应增加，而单核细胞数量减少，表明 T 细胞和 B 细胞反应的快速适应性协调以及不同程度的炎症。因此，儿童先前的 β-冠状病毒免疫力降低和 T 细胞活化减少可能会导致较温和的 COVID-19 发病机制。