SARS-CoV-2 specific T cell responses are lower in children and increase with age and time after infection Carolyn A. Cohen, Athena P. Y. Li, Asmaa Hachim, David S. C. Hui, Mike Y. W. Kwan, Owen T. Y. Tsang, Susan S. Chiu, Wai Hung Chan, Yat Sun Yau, Niloufar Kavian, Fionn N. L. Ma, Eric H. Y. Lau, Samuel M. S. Cheng, Leo L. M. Poon, Malik Peiris & Sophie A. ValkenburgNature Communicationsvolume 12, Article number: 4678 (2021) Cite this article6169 Accesses267 AltmetricMetricsdetails Abstract 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.
从症状轻的原因看来，儿童症状轻不意味着感染的病毒被杀死了，而是免疫系统反应小而已。
换句话说，如果是免疫系统过度反应造成的后遗症，儿童应该平均更轻；但如果是病毒本身造成的后遗症，由于儿童感染的病毒并没有被更多地杀死，后遗症平均不应该比大人轻。
https://www.nature.com/articles/s41467-021-24938-4
图太多，4张以外可以看上面的链接
SARS-CoV-2 specific T cell responses are lower in children and increase with age and time after infection Carolyn A. Cohen, Athena P. Y. Li, Asmaa Hachim, David S. C. Hui, Mike Y. W. Kwan, Owen T. Y. Tsang, Susan S. Chiu, Wai Hung Chan, Yat Sun Yau, Niloufar Kavian, Fionn N. L. Ma, Eric H. Y. Lau, Samuel M. S. Cheng, Leo L. M. Poon, Malik Peiris & Sophie A. Valkenburg Nature Communications volume 12, Article number: 4678 (2021) Cite this article 6169 Accesses 267 Altmetric Metrics details Abstract 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.
abstract就是summary 儿童对sars-cov-2的T细胞反应小。另外，儿童在感染前对其他Beta冠状病毒的免疫性更少（就是没有感染过，成人感染过类似的）。这两者造成儿童得sar-cov-2以后症状轻。
从症状轻的原因看来，儿童症状轻不意味着感染的病毒被杀死了，而是免疫系统反应小而已。
换句话说，如果是免疫系统过度反应造成的后遗症，儿童应该平均更轻；但如果是病毒本身造成的后遗症，由于儿童感染的病毒并没有被更多地杀死，后遗症平均不应该比大人轻