FIG. 4.

Cyclin D3 is required for affinity maturation but is dispensable for early Ag-specific antibody production. bWT (•) and bCcnd3^−/− (▴) animals were immunized i.p. with NP-KLH in CFA, and serum was collected at the indicated time points. Total Ag-specific IgM and IgG (A), and affinity maturation (B), determined by the ratio of high-affinity IgG to Ag-specific IgG, was measured by ELISA. The data shown is from four independent experiments with three to five mice per group. (C and D) The generation of IgG class switched B cells from GL7⁺ and GL7⁻ GC B cells (B220⁺, PNA⁺) 14 days postimmunization was measured by flow cytometry. IgG1⁺ cells are represented as a percentage of PNA⁺ B cells. The data from five animals are shown. Graphs show means and SEM, along with the P value, as determined by using an unpaired t test.