Fig. 2
From: SARS-CoV-2 spike-specific TFH cells exhibit unique responses in infected and vaccinated individuals
Kinetics of spike-specific antibody responses in COVID-19 convalescents. a Endpoint titers and (b) avidity index of plasma spike-specific IgG, IgG1, IgG3, and IgA antibodies among COVID-19 convalescents at 2 months (n = 25), 5 months (n = 25), 8 months (n = 25), 12 months (n = 24), and 24 months (n = 5) after illness onset. The endpoint titer data were logarithmically transformed. c Neutralization titers of COVID-19 convalescent plasma against SARS-CoV-2 pseudotyped virus at the indicated time points. The cut-off value was defined as ID50 = 30, and samples with an ID50 > 30 were considered to have a neutralizing effect. For (a–c), data are presented as median ± IQR (25–75%). Mann–Whitney U test was used to analyze the differences between the indicated time points, *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. P < 0.05 was considered to be a two-tailed significant difference, ns, not significant. d–e Correlations of frequencies of spike-specific TFH cells, CXCR3+ TFH cells, and CXCR3− TFH cells (data presented with background subtracted) with IgG and IgA endpoint titers at 5 months after illness onset (n = 17). Spearman’s rank correlation coefficient was used to describe the association between the frequency of TFH cells and subsets with the IgG or IgA endpoint titers. P < 0.05 was considered to be a two-tailed significant difference
