COVID-19 induced immunosuppression leading to secondary infection in a non-HIV patient

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As of now, the mechanism of lymphopenia, both CD4+ and CD8+ T cell count drops, in COVID-19 needs further study. Firstly, lymphopenia may be caused by increased cell death. An interesting study performed a transcriptomic RNA-sequencing analysis in COVID-19 patients with lymphopenia and found that apoptosis and p53 cell death pathways were activated in lymphocytes of COVID-19 patients when compared to healthy individuals.2 Secondly, cytokines or hypercytokinemia may play a role in lymphopenia in COVID-19. Proinflammatory cytokines such as TNF-alpha have been shown to cause lymphopenia by suppressing hematopoiesis.3 Also, SARS-CoV-2 virus may be capable of entering T lymphocytes by binding to a T cell surface protein such as CD147 and may cause a direct cytopathic effect to lymphocytes.4 Other possible mechanisms of lymphopenia in COVID-19 that need further study include lymphocyte exhaustion, possible bone marrow suppression by cytokines, or sequestration of lymphocytes in the lung with extensive infection.3, 4 References

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