Fig. 2.

Summarization of various immune responses against COVID-19. PRRs identify PAMPs and DAMPs in the innate immune response, causes macrophage activation and the release of inflammatory cytokines. T and B cells are also activated, and differentiation is aided. T cells come in a variety of subtypes that release cytokines. IL-1β activates neutrophils, causing them to produce IFN-γ, TNF-α, perforin, granzymes, as well as activates DCs. Infected epithelial cells may give virus antigens to naïve T cells (TH0), which then release IL-12 and differentiate into TH1 (CD4 + T cells) and TH2 (CD8 + T cells). Apoptosis occurs when NK cells become cytotoxic to virus-infected epithelial cells. DCs and macrophages use the MHC-TCR interaction to present viral antigen to CD4 + T cells. Memory T cells are developed, and they may confer protection against reinfection with the same viral strain for a period of time that has yet to be determined. The activated B cell also acts as an APC, presenting the antigen to the TH2 cell via MHC-II and TCR interaction. The TH2 cell then generates IL-4, IL-5, IL-6, IL-10, and TGF-β, while the B cell differentiates into plasma cells and memory B cells, which produce anti-SARS-CoV-2 specific IgM, IgA, and IgG antibodies