IL33 and influenza: Interestingly, activation of B1 cells during filarial nematode pleural infection was shown to depend on a IL-33-ILC2-IL-5 axis [24] that appears analogous to the one we describe here for the first time but with some important differences: the subtype of ILC2 activated (IL-33-responsive nILC2 rather than IL-25-responsive iILC2) and the fact that B1 cells and IgM production remained localized to the respiratory lymphoid structures, as observed during influenza infection, in contrast to systemic IgM and B1 cells migration to spleen observed in our model.