Thymi, spleen and Peyer’s patches (PPs) were isolated from mice. Spleen and thymi single-cell suspensions were generated as described above. PPs were pressed through a 70-μm nylon screen to generate a single-cell suspension. Single-cell suspensions were stained for 30 min at 4 °C with the indicated antibodies. Staining for CD40L was performed as previously described (58 (link)). For intracellular Ig H + L staining, the BD Cytofix/Cytoperm kit was used as per the manufacturer’s instructions. For intranuclear transcription factor staining, the Tonbo Foxp3 / Transcription Factor Staining Buffer Kit was used as per the manufacturer’s instructions. Samples were acquired with a BD LSRII or Fortessa X-20 (BD Biosciences) and analyzed with FlowJo version 10.8.1 (FlowJo LLC).