Table 2.
Characteristics and function of Tfh cells in COVID-19 patients.
| Severity of disease | Characteristics | Function | Isotype of antibodies | References |
|---|---|---|---|---|
| Convalescent | CD3+CD4+CD45RA-CXCR5+Tfh cells expansion; bias to a CCR6+CXCR3-cTfh17 cells. | Positively associate with plasma neutralizing activity. | — | (146) |
| cTfh-em and cTfh1 cells expansion. | Positively associate with the SARS-CoV-2-specific antibody titers. | IgM | (149) | |
| Mild | CXCR5+ICOS+PD-1+cTfh cells expansion, | Correlate with better clinical outcomes. | IgM, IgG | (144) |
| CD45RA-PD-1+CXCR5+cTfh cells reduction, activated cTfh (CD38+ICOS+) cells expansion. | Positively correlate with anti-SARS-CoV-2IgM and IgG titers. | IgM, IgG | (153) | |
| Moderate | TIM-3+Tfh-like cells expansion, CD226+Tfh-like cells reduction. | Benefit the maintenance of balanced cellular and humoral immune responses. | — | (155) |
| Severe | Tem and Tfh-em cells expansion, Tcm, Tfh-cm, and Tfr cells reduction. | cTfh-em cells negatively correlate with recorded PaO2/FiO2. | IgG, IgA | (149) |
| Cytotoxic cTfh cells and cytotoxic T helper cells expansion, Treg cells reduction. | Negatively correlate with antibody levels to SARS-CoV-2spike protein. | — | (154) | |
| PD-1+ICOS+CXCR5+CD4+cTfh cells expansion. | Correlate with robust humoral immunity. | IgG, IgM, and IgA | (159) | |
| CCR6+cTfh cells and CCR4+cTfh cells expansion, CCR3+cTfh cells and Th1 cells reduction. | Favor the development of the antibody response. | — | (162) |
“—” indicates not mentioned; Tfh, follicular helper T cell; cTfh, circulating Tfh cell; cTfh-em, effector-memory-like circulating Tfh cell; Tfh-cm, central-memory-like circulating Tfh cell; Tfr, follicular T regulatory cell; PaO2, arterial oxygen tension; FiO2, inspiratory oxygen fraction;Treg, regulatory T cells.