Innate and Adaptive Immunity Imbalance With Severe COVID-19 Pneumonia in Children and Adults.

Introduction: Little is known about the laboratory and radiological characteristics and clinical significance of peripheral immune alterations in patients with coronavirus disease 2019 (COVID-19). This study aims to clarify these aspects in children and adults with COVID-19. Methods: In this consecutive pilot study, COVID-19 patients with the confirmed pneumonia and real-time RT-PCR were recruited prospectively in June 2020. The clinical, chest CT, and laboratory features, such as lymphocyte subpopulations, were analyzed for each individual. Results: Forty confirmed COVID-19 patients, 11 severe children, 12 severe adults, and 17 critical adult patients, besides 20 healthy pediatrics and 14 healthy adults as controls, were enrolled prospectively. Adult patients, especially critical ones, had a much higher prevalence of laboratory and chest CT abnormalities. Data regarding immune cell subsets in children patients, compared with matched controls, had higher CD3+ CD8+ T cells (p = 0.004) and lower CD4+/CD8+ ratio (p = 0.042), while adult patients, compared with matched controls, had lower CD14+ monocytes (p = 0.032). Adult patients were also categorized as experiencing critical or severe illness on admission and, compared with severe patients, had lower total lymphocytes (p < 0.047), CD3+ T-lymphocytes (p < 0.002), and CD3+ CD8+ T cells (p = 0.001) and, on the other hand, had higher CD3+ CD4+ T cells (p = 0.012) and CD4+/CD8+ ratio (p = 0.003). Non survived adults, compared with survived patients, had significantly lower CD3+ T-lymphocyte (p = 0.005). Conclusion: Unlike adult patients, who compared with matched controls and had more comorbidities, higher frequency of severe clinical symptoms, laboratory abnormalities, and immune cells alteration, clinical manifestations of COVID-19 in children (compared with matched controls) were relatively mild, and fewer clinical complications were seen either, perhaps because of a milder inflammatory response following their peripheral innate and adaptive immune cell alteration pattern.