Development and functional analysis of B cells from Par-4 transgenic and nontransgenic littermates. (A-C) Bone marrow (A), spleen (B), and peritoneal cavity aspirate (C) from transgenic (Par-4) and nontransgenic (WT) individuals were stained for various B-cell markers and analyzed by flow cytometry. Dot plots gated on live B cells are shown from representative animals (n = 4). Populations of mature (CD43⁻IgM⁺IgD⁺), immature (CD43⁻IgM⁺IgD⁻), pro- (CD43⁺CD24^Int), pre- (CD43⁺CD24⁺), marginal zone (CD21/35⁺CD23⁻IgD⁻), follicular (CD21/35⁺CD23⁺IgD⁺), B1a (CD11b⁺CD5⁺), B1b (CD11b⁺CD5⁻), and B2 (CD11b⁻CD5⁻) B cells were then determined. (D) Splenic B cells isolated from transgenic and nontransgenic animals (n = 6 per group) were stimulated with anti-mouse IgM, LPS, CpG, or PMA + ionomycin and incubated in the presence of tritiated thymidine for the indicated number of hours. Incorporated thymidine was determined as counts per minute (CPMs) and is shown as means for each group, with error bars indicating standard error of the mean. (E) Basal serum levels of IgM, IgA, IgG1, IgG2a, IgG2b, and IgG3 in transgenic (Tg; Par-4) and nontransgenic (NTg; WT) mice as determined by enzyme-linked immunosorbent assay. Bars represent mean serum concentrations of the indicated isotype (n = 12). DMSO, dimethyl sulfoxide.