Previous research has underscored the pivotal role of IL-17 and Tfh17 in GC B cell activation,47 as well as the generation and sustainability of LLPCs, particularly in systemic lupus erythematosus (SLE).48–50 Moreover, compared to Tfh1 and Tfh2 cells, Tfh17 cells have a stronger tendency to induce LLPCs generation.51 Interestingly, similar Th17 biased CD4+ T cell responses have been observed in another flagellin-based mucosal vaccine, P-KFD1.23 The co-localization of IL-17 with the plasma marker CD138 (Fig. 3) suggested a link between the vaccine-induced LLPCs and the Th17 biased responses. Here, CD4 is linked to systemic lupus erythematosus.