Fig. 1

SARS-CoV-2 antigen-specific CD8+ T cells, CD4+ T cells, and neutralizing antibodies. a Troika combating COVID-19 infection. A coordinated response involving CD8⁺ cytotoxic T cells, CD4⁺ helper T cells, and neutralizing antibodies is required to provide the best protective effects for SARS-CoV-2 infections. However, in older patients whose CD8⁺ T and CD4⁺ T cell responses are compromised, the diseases are prone to progress to severe stages