3.1. Natural immunity
The SARS-CoV2 like the other member of coronavirus family is habitually
reluctant to stimulate innate immune cells such as dendritic cells and
hamper the antiviral type I and III interferon responses [8]. So,
thwarting the innate immune responses by SARS-CoV-2 leads to the
prolongation of incubation period and smooth transmission of the
pathogenic agent without clinical symptoms [9]. Besides the eruptive
replication of the SARS-CoV2 virions in the early stages of the disease
corroborant of the slant innate immunity and considered as a foundation
for ensuing cytokine storm complications especially in severe COVID-19
patients [10]. So, the infected patients experienced elevated
circulatory levels of inflammatory cytokines and chemokines, enhanced
overactivated blood monocytes and neutrophils [11, 12] and M1
macrophages accumulation in the lung which derived from
CD14+/CD16+ proinflammatory
monocytes [13]. Also, lack of early restriction of SARS-CoV2
replication in the airways by innate immunity leads to viral overload
and resultant hyper inflammatory syndromes including acute respiratory
distress syndrome (ARDS) [8].