Introduction
The Coronavirus Disease 2019 (COVID-19) caused by severe acute
respiratory syndrome corona virus 2 (SARS-CoV-2) has rapidly spread in
China and around the world and is still on-going
(Sohrabi, Alsafi et al. 2020). All
people, including children are susceptible to SARS-CoV-2, and a rapid
progression in morbidity and mortality rate due to human-to-human
transmission of the virus are still reported
(Lotfi and Rezaei 2020).
Although the pathogenesis of COVID-19 is not fully described, the
interaction between the SARS-CoV-2 and the immune system is so
complicated, and lymphopenia, hyper-inflammatory responses, and
cytokines play an important role in the pathogenesis of COVID-19
(Saghazadeh and Rezaei 2020,
Yazdanpanah, Hamblin et al. 2020).
Recent studies suggest that the SARS-CoV-2 infection may primarily
affect T lymphocytes, particularly CD4+ T and
CD8+ T cells, which might be highly involved in the
pathological process of COVID-19 (Henry, de
Oliveira et al. 2020, Wang, Hu et al.
2020).
CD4+ and CD8+ T cells play a fundamental role in controlling viral infections maintaining
cellular and humoral immune responses. These cells are involved in
humoral and cytotoxic immunity against viral infections.
CD4+ T cells have multiple roles and are required to
support CD8+ T cell responses. Moreover, these cells
help to B cells to elicit antibody responses
(Ng, Snell et al. 2013).
CD8+ T cells have been shown to play a critical role
in mediating viral clearance after acute viral respiratory infections,
including respiratory syncytial virus, influenza A virus, and human
metapneumovirus (Wang, Nie et al. 2020).
Among the laboratory features of COVID-19, a number of hematological
abnormalities have been described (Henry,
de Oliveira et al. 2020); however, no studies about lymphocyte subset
analyses have been reported in children. Therefore, it is important to
explain the characteristics of lymphocyte subsets in pediatrics with
mild or severe COVID-19. This study aimed to evaluate the lymphocyte
subsets in 55 laboratory-confirmed cases of SARS-CoV-2.