Fig. 2. Th cellular immunity during Omicron and Delta BTI.

Omicron or Delta BTI vaccinated healthy donors or SARS-CoV2 WT convalescents were analyzed to quantify their frequency and characterize the phenotypes of CD4⁺ T_FH cells (a–c) or to assess their functions (e, f). a Mass Cytometry profile of CXCR5⁺CD4⁺ Follicular helper T cells. Visualization by tSNE-plot of clusters automatically identified by Phenograph in total T_FH from concatenated files of vaccinated HD, Omicron BTI, and Delta BTI (see Methods and Supplementary Fig. 6 legend for details). b The absolute frequency of T_FH CD4 T cells in PBMCs for all BTI patients. c Frequency of T_FH cells expressing memory (CD95) or activation markers (HLA-DR), PD-1, and chemokine receptors (CCR4, CCR6, CXCR3). d Functional responses of SARS-CoV-2 specific CD4⁺ T cells. The specific responding CD4⁺ T cells are shown similarly as in Fig. 1f. e Biplot showing in vitro responses of CD4⁺ T cells to non-Spike peptide pools vs. Spike-peptides as described²⁸: infected and nonvaccinated (I⁺V⁻), non-infected and vaccinated (I⁻V⁺); or infected and vaccinated (I⁺V⁺). Mann–Whitney test P values are shown for (b–d). See also Supplementary Fig. 6.