Literature Review (Grey)
The adaptive immune system is important for control of most viral infections. The three fundamental components of the adaptive immune system are B cells (the source of antibodies), CD4+ T cells, and CD8+ T cells. The armamentarium of B cells, CD4+ T cells, and CD8+ T cells has differing roles in different viral infections, and following vaccination, and thus it is critical to directly study adaptive immunity to SARS-CoV-2 to understand COVID-19. Knowledge is now available on relationships between antigen-specific immune responses and SARS-CoV-2 infection. While more studies are needed, a picture has begun to emerge that reveals that CD4+ T cells, CD8+ T cells, and neutralising antibodies all contribute to control of SARS-CoV-2, in both non-hospitalised and hospitalised cases of COVID-19.
In this review article, the specific functions and kinetics of these adaptive immune responses are discussed, as well as their interplay with innate immunity, implications for COVID-19 vaccines and immune memory against re-infection.