Constitutive CD30 expression in B cells leads to the expansion of B1 cells and PCs. (A) Splenic weights and absolute splenic B- and T-cell numbers from LMP1/CD30 mice and controls (ctrl) age 8 to 12 weeks are shown. (B) Splenic sections from LMP1/CD30 and ctrl mice were stained for immunoglobulin M (IgM; brown/red), CD3 (light blue), and MOMA-1 (dark blue) to visualize B cells, T cells, and metallophilic macrophages, respectively. Slides were analyzed with an Axioskop (Zeiss) with a Zeiss Plan NEOFLUAR (objective 10×/0.3). Images were obtained with an AxioCam MRc5 digital camera in combination with AxioVision rel.4.6.3.0 software (Carl Zeiss MicroImaging GmbH, Jena, Germany). (C) Splenic B lymphocytes (CD19⁺) were analyzed for the expression of IgM/IgD, distribution of follicular B cells (CD21^intCD23⁺) and marginal zone B cells (CD21^highCD23^low), distribution of B1 (CD43⁺CD23^low) and B2 (CD43⁻CD23⁺) cells, and distribution of B1a (CD5⁺B220^low), B1b (CD5^lowB220^low), and B2 (B220⁺CD5^low) by flow cytometry (n ≥ 6). (D) Flow cytometric analysis of splenic and bone marrow lymphocytes stained for PCs (B220^−/lowCD138⁺). Cells were pregated using a large lymphocyte gate (n ≥ 6). Numbers in the fluorescence-activated cell sorting plots indicate the mean and standard deviation values of the percentages of the gated populations. (E) Total numbers of B lymphocytes (CD19⁺) in the PerC were counted and calculated based on their staining: B1a (CD5⁺B220^low), B1b (CD5^lowB220^low) and B2 (CD5^lowB220⁺). B cells from LMP1/CD30 mice were gated on hCD2. Data were collected from 8- to 16-week-old mice. *P < .05, **P < .01, ***P = .001, ****P < .0001.