?:abstract
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The outbreak of the SARS-CoV-2 virus in December 2019 has caused the deaths of several hundred thousand people worldwide Currently, the pathogenesis of COVID-19 is poorly understood During the course of COVID-19 infection, many patients experience deterioration, which might be associated with systemic inflammation and cytokine storm syndrome;however, other patients have mild symptoms or are asymptomatic There are some suggestions that impaired cellular immunity through a reduction in Th1 response and IFNG (interferon gamma) expression, as well as cross-reactivity with common cold coronaviruses, might be involved in the differential COVID-19 course Here, we show that CD4+ cells isolated from unexposed healthy donors that were differentiated towards the Th1 lineage in the presence of SARS-CoV-2 proteins exhibited induction of IFNG Interestingly, the same cells induced to differentiate towards a Th17 lineage did not exhibit changes in IFNG expression or Th17-related cytokines This suggests the cellular response to SARS-CoV-2 viral proteins is primarily associated with Th1 lymphocytes and may be dependent on past infections with common cold coronaviruses or vaccinations that induce unspecific cellular responses, e g , BCG (Bacillus Calmette-Guérin) Thus, our results might explain the high variability in the course of COVID-19 among populations of different countries
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