We previously used the transgenic CD19-Cre PD-L2-ZsGreen-TdTomato-diphtheria toxin receptor (PZTD) mouse line, which operates as both an inducible-depletion system and as a fluorescent reporter to show that 28 days after 2 pneumococcal infections, PD-L2+ B cells are only present in the EV spaces of the lung, where they function as protective BRM cells (14, 64). The gene discussed is CD19; the disease is pneumococcal infection.