Transcriptomic analysis by scRNA-seq, flow cytometry, histology, ELISA and the use of knock out mice, demonstrates the rapid and terminal differentiation of B220+CD21highCD1d+IgM+ Marginal Zone B cells (MZBs), and B220+CD23highIgD+IgMInt Follicular B cells (FoBs) into IgM and IgG2c secreting plasma cells (PCs), independently from losing splenic B follicles during infection. Here, CD40LG is linked to infection.