Long-lived plasma cells and memory B cells are absent in immunized Dicer1^fl/flAicda^Cre/+ mice. (A) Flow cytometric analysis of NP-specific IgG1 memory B cells in the spleen of mice 56 days after immunization with NP₃₈-CGG. Splenic cells were stained for B220, IgG1, and CD38 expression and NIP binding after exclusion of dead cells (4,6-diamidino-2-phenylindole), non-B cells (Dump), and IgM⁺ cells. The numbers adjacent to the outlined areas indicate the percentage of gated cells (upper panel) and the absolute number of cells per 1 × 10⁴ IgM⁻Dump⁻B220⁺ cells (bottom panel). (B) NIP-binding CD38⁺IgG1^hi memory B cells in the spleens of Dicer1^+/+Aicda^Cre/+ (●) and Dicer1^fl/flAicda^Cre/+ mice (○) mice 56 days after immunization. (C) ELISPOT assays of anti–NP IgG1 ASCs cells in the bone marrow of day 56 postimmunized Dicer1^+/+Aicda^Cre/+ and Dicer1^fl/flAicda^Cre/+ mice using BSA-NP₁₇ as coating antigens. (D) Anti–NP IgG1 ASCs in the bone marrow of Dicer1^+/+Aicda^Cre/+ (●) and Dicer1^fl/flAicda^Cre/+ (○) mice 56 days after immunization were quantified by ELISPOT assay. Each symbol represents 1 mouse.