Figure 1. The expression levels of CD23 are reduced in isotype switched and memory B cells compared to follicular unswitched B cells.

The expression levels of CD23 in indicated B-cell subsets from a representative mouse 100 days post first immunization were determined using flow cytometry. Splenic B cells were isolated from non-immunized mice and mice 100 days post the first immunization with NP-KLH and Ribi adjuvant. Cells were stained with FITC-anti-IgD, FITC-anti-IgM, PE-anti-CD138, PerCP-Cy5.5-anti-B220 Abs and allophycocyanin-NP₁₉ (A). B-cell subsets were identified by specific surface markers: NP-binding memory B cells (Memory) B220⁺ CD138⁻ IgM⁻ IgD⁻ NP⁺, NP-binding unswitched follicular B cells (Ag⁺ FO) B220⁺ CD138⁻ IgM^int IgD⁺ NP⁺, naïve follicular B cells (FO) B220⁺ CD138⁻ IgM^int IgD⁺ NP⁻ (A,B). Shown are representative histograms (C), the dot blot to show the gating stretagy(A and B), and the average (±SD) of the mean fluorescence intensity (MFI) of CD23 in follicular B cells from non-immunized mice (non-im), and follicular isotype unswitched (IgD⁺) and switched (IgD⁻IgM⁻) B cells (D), and NP⁺ or NP⁻ B cells (E) from immunized mice. n = 4. **p < 0.01.