Cross-tissue single-cell analysis reveals transcriptional and functional diversity of T follicular helper cells from infancy to adulthood 3741

Abstract Description T follicular helper (Tfh) cells play a crucial role in humoral immunity by fine-tuning the quality of neutralizing antibodies (nAbs). However, they are mostly restricted to tissue sites, making them challenging to study in the context of vaccination. In this study, we used spleens, lymph nodes, and tonsils collected from humans (n = 30, ages 2-58 years) to comprehensively profile the diversity of Tfh ex vivo using flow cytometry and single cell transcriptomics. Multimodal analyses revealed that Tfh were enriched and were more clonal in young children, but their cytokines responses to ex vivo stimulation and polarized phenotypes (Tfh1, Tfh2, and Tfh17 associated) increased with age. Next, we used the tonsil immune organoid system to dissect Tfh responses to ex vivo vaccination with influenza antigens. Single cell analyses revealed early proliferation and heightened Tfh activation in young children compared to adults. Frequencies of activated Tfh1 strongly correlated with nAbs in both groups. Depleting Tfh in organoids reduced germinal center (GC) B cell frequencies but did not alter the expansion of antigen-specific B cells. While overall antibody magnitude remained unchanged, nAbs were attenuated with Tfh depletion in adults but remained unchanged in children. These findings suggest that Tfh play distinct functional roles in GCs in children versus adults. Ongoing investigations are focused on understanding how Tfh regulate affinity maturation in GCs in different age groups. Funding Sources Supported by NIH/NIAID 1R01AI173023; NIH/NIAID 1U01AI180164; Wellcome LEAP (Wellcome Trust, UK); Bill and Melinda Gates Foundation Topic Categories Computational and Systems Immunology (COMP)