antibodies – CD4 APCCy7 (RPA-T4, BD Biosciences), CXCR5 Alexa 488 or
Alexa 647 (RF8B2, BD Biosciences), PD-1 PE (MIH4, eBioscience) or BV605 or BV421
(EH12.2H7, BioLegend), CD127 FITC (11-1278, eBioscience) or BV 421 (A019D5,
BioLegend), CD25 biotin (BC96, eBioscience or BioLegend) or PE-Cy7 (BC96, BD
Biosciences or BioLegend), BCL6 Alexa 647 or PE-Cy7 (K112-91, BD Biosciences),
CD3 APC (HIT3a, BD Biosciences) or Alexa 700 (UCHT1, BD Biosciences), CD27 FITC
or APC (M-T271, BD Biosciences), CD38 FITC (HIT2, BD Biosciences) or PE (HB7, BD
Biosciences), ICOSL APC (2D3, BioLegend), FAS PE-CF594 (DX2, BD Bioscience),
CD40 APCCy7 (5C3, BioLegend), BAFFR PECy7 (11C1, BioLegend), CD19 PECy7 or BV605
(SJ25C1, BD Bioscience), IL21R BV421 (17A12, BioLegend), CD86 BV421 (2331/FUN-1,
BD Bioscience). All surface stains were performed in the presence of Human
TruStain FcX (cat. 422302, BD Bioscience). Intracellular staining was performed
using the FOXP3/Transcription Factor Staining Buffer Set (eBioscience) according
to the manufacturer’s instructions. Cells were stained with primary
antibodies followed by secondary reagents for 30 min at 4 °C. Data were
collected on a LSRII or Fortessa cytometer (BD) and analysed with FlowJo
software (TreeStar). 7-AAD (Invitrogen) or Zombie Aqua (BioLegend) staining was
used to exclude dead cells from analysis.