FIG. 3.

Purified B lymphocytes were specifically stimulated by purified H. pylori urease. (A) Enriched CD3⁻ CD14⁻ B220⁺ B lymphocytes with >90% purity were obtained reproducibly by the procedure described in Materials and Methods. (B) Using 10⁶ of these purified B lymphocytes, we confirmed their significant proliferative responses when the cells were cocultured with 10-μg/ml purified H. pylori urease, whose stimulatory activity was not blocked at all by the addition of 20-μg/ml polymyxin B, a known lipid A antagonist. In contrast, when the B cells were stimulated by 10-ng/ml E. coli-derived LPS, the stimulatory activity was specifically abrogated by the addition of 20-μg/ml polymyxin B. Data are expressed as the mean counts per minute ± SEM of three independent experiments.