Extended Data Figure 1. Phosphatidylinositol 3-Kinase (PI3K)δ blockade increases AID expression and CSR in activated mouse B cells.

a, Schematic representation of the in vivo experiment in WT mice immunized with sheep red blood cells (SRBCs) and treated with the indicated inhibitors (n = 6 biological replicates). b, Representative dot plots of IgG₁ switched GL7⁺/B220⁺ germinal center (GC) B cells from mice treated with vehicle or the PI3Kδ inhibitors. c, Mean IgG₁ CSR analyzed by flow cytometry in control and idelalisib or duvelisib treated mice. Data are expressed as mean ± s.d. (n=3). ** P ≤ 0.01, two-tailed Student’s t-test. d,e, IgG₁ CSR analyzed by flow cytometry in activated B cells treated with 0.5 μM (d) or 0.1 μM (e) of the indicated drugs. Data are expressed as mean ± s.d. (n=3). * P < 0.05, ** P ≤ 0.01, *** P ≤ 0.001, two-tailed Student’s t-test f, Western blot for AID protein expression in activated B cells treated with the indicated inhibitors (0.1 μM) (n = 3 biological replicates). For gel source data, see Supplementary Figure 1. g, Viable cells were counted at the indicated time points by Trypan Blue exclusion in activated B cells treated with the indicated inhibitors (1 μM). Data are expressed as mean ± s.d. (n=3). P values calculated by two-tailed Student’s t-test. h, Representative western blot for AID and PI3K p110δ protein expression in mouse B cells transduced with retrovirus expressing PI3K p110δ^WT or the p110δ^E1021K active mutant (n = 4 biological replicates). i, Aicda mRNA levels analyzed by qRT-PCR in activated B cells transduced with PI3K p110δ^WT or the p110δ^E1021K active mutant. Data are expressed as mean ± s.d. (n=3). P values calculated by two-tailed Student’s t-test by comparing PI3K p110δ^E1021K vs PI3K p110δ^WT cells. j, IgG₁ CSR analyzed by flow cytometry in activated B cells expressing PI3K p110δ^WT or the p110δ^E1021K active mutant. Data are expressed as mean ± s.d. (n=3). * P < 0.05, ** P ≤ 0.01, two-tailed Student’s t-test