Genotyping of Bcl6 Knockout Mice

All animal work was conducted in accordance with the UK Home Office and the local AWERB committee (UK Home Office project license P996A24e1). Specific pathogen–free 6- to 8-wk-old or pregnant female BALB/c and C57BL/6 mice were purchased from Charles River Laboratories. 6- to 10-wk-old B6.129S-Bcl6^tm1.1Dent/J (Bcl6^fl) mice (Hollister et al., 2013 (link); stock number 023727) were purchased from The Jackson Laboratory and bred with B6.Cg-Tg(Cd4-cre)1Cwi/BfluJ (CD4Cre) mice (Lee et al., 2001 (link); stock number 022071; kindly provided by Professor Matthias Merkenschlager, Imperial College London, London, UK) at Central Biomedical Services (Imperial College London, UK) and Charles River Laboratories (Margate, UK). Genotypes were determined using DNA extracted from ear biopsies processed using Extract-N-Amp Tissue PCR Kit (Sigma-Aldrich), amplified by PCR, and separated by gel electrophoresis according to the Bcl6^fl and Generic Cre protocols provided by The Jackson Laboratory; custom PCR primers were purchased from Sigma-Aldrich.