T1 B cells are short-lived in culture although survival can be improved by coculture with mouse bone marrow stromal cells or IL-4 but not BAFF. (A) Negatively selected peripheral blood B cells from healthy adult donors were stained with anti-CD20, anti-CD10, and anti-CD44 or anti-CD19, anti-CD24, and anti-CD38. T1 B cell (CD20^hi CD10^hi CD44^lo or CD19⁺ CD24^hi CD38^hi), mature naive (Mat) (CD20⁺ CD10^- CD44^hi or CD19⁺, CD24^lo, CD38^lo) and intermediate (Int) (CD20⁺ CD10^lo CD44^hi or CD19⁺ CD24^int, CD38^int) B-cell populations were sorted as shown. Postsorting analysis indicated that each population was more than 95% pure. (B) T1 and mature B-cell populations were cultured for 24 hours and stained with annexin V and 7-AAD. (C) T1 B cells, intermediate and mature B cell populations were cultured in medium alone or with the addition of either BAFF (200 ng/mL), IL-4 (100 ng/mL), or cultured on mouse S13 bone marrow stromal cells. After 24 hours or 3 days in culture, the cells were examined for viability by flow cytometry using forward/side scatter characteristics or 7-AAD exclusion. The data show the means ± SEM of at least 4 independent experiments. Unpaired t tests were used to detect significant differences (^*P <.05; ^**P <.01).