Fig 1: CXCR3 expression on plasmablasts is induced by via IFNγ from PD-1highCXCR5– Tph cells(A) T cells (n = 5, patients with COVID-19) were stimulated with anti-CD3/28 for 48 h, then cytokine productions were measured (IFNγ, IL-10) by ELISA.(B) IL-21 and CXCL13 levels in the supernatants of co-cultures were measured by ELISA (n = 7, patients with COVID-19).(C and D) CD20+CD27+ memory B cells (n = 5, healthy controls) were cultured with CD40L, IL-21, and IL-10 or different concentrations of IFNγ for 7 days (n = 5, healthy controls). Representative histogram for CXCR3 expression on plasma cells (C, left) and CXCR3 gMFI was evaluated (C, right). After 7 days in culture, CD19+CD27+CD138+ plasma cells were sorted, and CXCR3 expression was measured by qPCR (D).(E) Representative data of CXCR3 expression on CD27highCD138+ plasma cells after co-culture with Tph cells (n = 5, patients with COVID-19) with anti-human IFNγ antibodies (anti-IFNγ Abs) or IgG isotype controls (IgG control) (E, top). CXCR3+CD27highCD138+ plasma cells (bottom) were evaluated by Wilcoxon matched-pairs signed rank test (E, bottom).(F) After 7 days culture of CD20+CD27+ memory B cells (n = 5, healthy donors) with various conditions, gene expressions of CD19+CD27highCD138+ plasma cells were measured by qPCR (n = 5, healthy controls).Data were evaluated by one-way ANOVA with Tukey’s multiple comparisons tests (A–D and F). Data are represented as mean ± SEM (A–D and F).