Expression of lineage markers within the expanded E/P^−/− lymph node B cell compartment.

(A) Non-B (CD5⁺/Mac-1⁺) cells were depleted from E/P^−/− and control cervical lymph nodes as described in “Materials and methods.” Examination of B220 and surface IgM expression by flow cytometry revealed 3 distinct B-cell populations present in E/P^−/− lymph nodes (indicated as I, II, and III), but only the normal IgM⁺ B cells in wild-type lymph nodes. (B) Three-color flow cytometry analysis was performed to further characterize the 3 E/P^−/− B-cell populations. The histograms show expression of CD19, CD38, syndecan-1, MHC class II, CD43 (S7), CD43 (S11), CD45, and an isotype control antibody on population I (black line), population II (gray line), and population III (filled). A representative experiment of at least 6 is shown. Fourteen total experiments examined syndecan-1 expression of population III cells resulting in an overall mean of 42.5% ± 25.9% positive. One representative experiment is shown.