Distinct mitochondria-mediated T cells apoptosis responses in children and adults with COVID-19

Yang, Yang; Liangjian, Kuang; Li, Linhai; Yongjian, Wu; Zhong, Bei; Huang, Xi

BACKGROUND: Lymphopenia is a key feature for adult patients with coronavirus disease 2019 (COVID-19), while it is rarely observed in children. The underlying mechanism remains unclear. METHODS: Immunohistochemical and flow cytometric analyses were used to compare the apoptotic rate of T cells from COVID-19 adults and children and apoptotic responses of adult and child T cells to COVID-19 pooled plasma. Biological properties of caspases and reactive oxygen species were assessed in T cells treated by COVID-19 pooled plasma. RESULTS: Mitochondria apoptosis of peripheral T cells were identified in COVID-19 adult patient samples, but not in the children. Furthermore, increased TNF-α and IL-6 in COVID-19 plasma induced mitochondria apoptosis and caused DNA damage by elevating reactive oxygen species levels of the adult T cells. However, the child T cells showed tolerance to mitochondrial apoptosis due to mitochondria autophagy. Activation of autophagy could decrease apoptotic sensitivity of the adult T cells to plasma from COVID-19 patients. CONCLUSIONS: Our results indicated that the mitochondrial apoptosis pathway was activated in T cells of COVID-19 adult patients specifically, which may shed light on the pathophysiological difference between adults and children infected with SARS-CoV-2.