Abstract
COVID-19 caused by the SARS-CoV-2 virus, accompanies an unprecedented spike in cytokines levels termed cytokines release syndrome (CRS), in critically ill patients. Clinicians claim that the surge demonstrates a deregulated immune defence in host, as infected cell expression analysis depicts a delay in type-I (interferon-I) and type-III IFNs expression, along with a limited Interferon-Stimulated Gene (ISG) response, which later resume and culminates in elicitation of several cytokines including- IL-6, IL-8, IL-12, TNFα, IL-17, MCP-1, IP-10 and IL-10 etc. Although cytokines are messenger molecules of the immune system, but their increased concentration results in inflammation, infiltration of macrophages, neutrophils and lung injury in patients. This inflammatory response results in the precarious pathogenesis of COVID-19; thus, a complete estimation of the immune response against SARS-CoV-2 is vital in designing a harmless and effective vaccine. In pathogenesis analysis, it emerges that a timely forceful type-I IFN production (18-24hrs post infection) promotes innate and acquired immune responses, while a delay in IFNs production (3-4 days post infection) actually renders both innate and acquired responses ineffective in fighting infection. Further, underlying conditions including hypertension, obesity, cardio-vascular disease etc may increase the chances of putting people in risk groups, which end up having critical form of infection. This review summarizes the events starting from viral entry, its struggle with the immune system and failure of host immunological parameters to obliterate the infections, which finally culminate into massive release of CRS and inflammation in gravely ill patients.