Introduction: In late December 2019, a sudden severe respiratory illness of unknown origin was reported in China. In early January 2020, the cause of COVID-19 infection was announced a new coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Examination of the SARS-CoV-2 genome sequence revealed a close resemblance to the previously reported SARS-CoV and coronavirus Middle East respiratory syndrome (MERS-CoV). However, initial testing of drugs used against SARS-CoV and MERS-CoV has been ineffective in controlling SARS-CoV-2. One of the key strategies to fight the virus is to look at how the immune system works against the virus, which has led to a better understanding of the disease and the development of new therapies and vaccine designs. Methods: This review discussed the innate and acquired immune system responses and how immune cells function against the virus to shed light on the human body's defense strategies. Results: Although immune responses have been revealed critical to eradicating infections caused by coronaviruses, dysregulated immune responses can lead to immune pathologies thoroughly investigated. Also, the benefit of mesenchymal stem cells, NK cells, Treg cells, specific T cells, and platelet lysates have been submitted as promising solutions to prevent the effects of infection in patients with COVID-19. Conclusion: It has been concluded that none of the above has undoubtedly been approved for the treatment or prevention of COVID-19, but clinical trials are underway better to understand the efficacy and safety of these cellular therapies.
