The data were unexpected, as we had shown previously that only the CD19+CD43+CD5+but not the CD5- B-1 cells were able to migrate from the pleural cavity to the MedLN after influenza infection, where they differentiated into IgM-secreting cells (Choi and Baumgarth, 2008; Waffarn et al., 2015). Here, CD19 is linked to influenza.