Figure 1.

Mathematical model of host immune response to SARS-CoV-2 infection

Solid arrow denotes either activation or differentiation. Dashed and blunt arrows denote migration and inhibition, respectively. Model variables include target healthy epithelial cells [H], infected cells [I], viral loads [V], dendritic cells [DC], antigen-presenting cells generated from DC at infection sites [APC_R] and in lymph nodes [APC_L], naive CD4⁺ and CD8⁺ T cells, [CD4⁺T₀] and [CD8⁺T₀], naive B cells [B₀], type-I helper T cells [Th1], T follicular helper cells [Tfh], cytotoxic T lymphocytes in lymph nodes [CTL_L] and infection sites [CTL_R], plasma B cells [pB], type-I interferon [IFN1], and immunoglobulin [Ig]. The typical flow in the immune response depicted in this figure is as follows: The healthy epithelial cells are infected by viral particles and become infected cells. The infected cells produce viral particles, also secreting IFN1 molecules (Sa Ribero et al., 2020). DC cells ingest viral particles and become working as APC_R cells. The APC_R cells secrete IFN1 molecules (Fitzgerald-Bocarsly and Feng, 2007). The APC_R cells migrate toward lymph nodes. The moved APC_R cells, namely, APC_L cells differentiate CD4⁺T₀ cells into Th1 and Tfh cells (Sette and Crotty, 2021), where IFN1 stimulates these developments (Cucak et al., 2009; Huber and Farrar, 2011). The APC_L and Th1 cells activate CD8⁺T₀ cells, which then differentiate into CTL_L cells (Swain et al., 2012). The CTL_L cells are recruited by IFN1 to migrate toward the sites of infection and the moved CTL_L cells, namely, CTL_R cells kill infected cells (Sette and Crotty, 2021). The APC_L and Tfh cells activate B₀ cells (Akkaya et al., 2020; Swain et al., 2012), which differentiate into pB cells, consequently Ig molecules are produced by the pB cells (Akkaya et al., 2020).