YY1 is required for germinal center B cell development and immunoglobulin class switching.

<p><b>(A)</b> Spleen cells from non-immunized <i>YY1</i>^<i>f/</i>, <i>γ1CRE</i> and <i>YY1</i>^<i>f/</i>f <i>γ1CRE</i> mice were stained with various antibodies to identify total B cells (CD19⁺AA4.1⁺, upper panel) and germinal center B cells (GC-B, DUMP^-IgD^-GL7^hiCD95^hi, lower panel). Percentages and number of <b>(B)</b> total B cells, and <b>(C)</b> GC-B cells per spleen of <i>YY1</i>^<i>f/</i>, <i>γ1CRE</i> and <i>YY1</i>^<i>f/</i>f <i>γ1CRE</i> mice. Fig A-C are from three independent experiments (<i>n</i> = 3 mice for each genotype). <b>(D)</b> We used ELISA to detect various isotypes of serum immunoglobulins from <i>YY1</i>^<i>f/</i>, <i>γ1CRE</i> and <i>YY1</i>^<i>f/</i>f <i>γ1CRE</i> mice. The concentration of IgM, IgA, total IgG, as well as IgG subclasses, IgG1, IgG2 and IgG3 were measured from sera samples that were obtained from four experiments (<i>n</i> ≥ 4 mice for each genotype). Asterisks indicate p<0.001.</p

YY1 is required for antigen-specific germinal center development and for generation of antigen-specific IgG1.

<p><b>(A)</b> Splenocytes from NP-CGG immunized <i>γ1CRE</i> and <i>YY1</i>^<i>f/</i>f <i>γ1CRE</i> mice were harvested at 14 days after immunization and stained with various antibodies, as well as PNA to detect GC B cells. We gated on CD4⁻CD8⁻F4/80⁻Gr1⁻(DUMP⁻) IgD^- cells that were subdivided into PNA⁺B220⁺ GC-B cells. GC-B cells were gated and further subsetted into NP-specific (NP⁺B220⁺) GC-B cells. Representative results are from three independent experiments. <b>(B)</b> Numbers of NP-specific (NP⁺B220⁺) GC-B cells per spleen of immunized mice (<i>n</i> = 3). <b>(C)</b> <i>γ1CRE</i> and <i>YY1</i>^<i>f/</i>f <i>γ1CRE</i> mice were immunized with NP-CGG, and 14 days later spleen sections were stained with anti-GL7, anti-IgD and anti-TCRβ antibody. GL7-rich regions demarcate germinal center B cells. <b>(D, E)</b> Serum from NP-CGG immunized <i>γ1CRE</i> and <i>YY1</i>^<i>f/</i>f <i>γ1CRE</i> mice were collected at 14 days after immunization and NP-specific serum Igs were analyzed using ELISA. <i>D</i>. The concentration of low affinity (NP26, left panel) and high affinity (NP4, right panel) IgG1 in the serum. <i>E</i>. Titer of NP-specific total IgM in the sera of immunized mice. Data are derived from sera samples that were obtained from three experiments. Asterisks indicate p<0.001.</p