Figure 4.

Temporal deletion of mammalian target of rapamycin complex 1 (mTORC1) signalling in early germinal centre (GC) development resulted in an impaired early humoral response. (a) Experimental set‐up for early GC induction of Rptor deletion. Aicda‐ERT2Cre‐YFP/Rptor ^flox (iR ptor‐KO) or control Aicda‐ERT2Cre‐YFP (CTL) mice were infected with the Armstrong strain of lymphocytic choriomeningitis virus (LCMV) and subsequently treated daily with tamoxifen via intraperitoneal injection during days 1–7 post‐infection. (b) Flow cytometry of lymphocytes in spleens of the CTL mice treated as described in (a) (left). The numbers above the outlined areas indicate the percentages of CD138⁺ plasma cells and B220⁺ B cells among YFP ⁺ cells (middle), and the percentage of IgD⁻ B cells among YFP ⁺ B220⁺ B cells (right). (c) Flow cytometry of YFP ⁺ B220⁺ B cells (top left), quantification of Rptor genomic DNA and mRNA in sorted YFP ⁺ B220⁺ CD95⁺ PNA ⁺ GCB cells (top right), quantification of total YFP ⁺ B220⁺ CD95⁺ PNA ⁺ GCB cell number per spleen and quantification of viability dye‐labelled dead GCB cell frequency and Ki67 in YFP ⁺ B220⁺ CD95⁺ PNA ⁺ GCB cells (bottom) in the spleens of the CTL and iR ptor‐KO mice treated as described in (a). (d) Flow cytometry of YFP ⁺ cells and quantification of total YFP ⁺ B220^mi/lo CD138⁺ plasma cell number in the spleen of the CTL and iR ptor‐KO mice treated as described in (a). *P < 0·05 **P < 0·005 ***P < 0·002 (unpaired two‐tailed t‐test). Data are representative of three independent experiments with three to six mice per group (error bars, SEM).