FIG. 2.
Acylation of r27 is crucial for its mitogenicity. (A) BALB/c splenocytes (4 × 105/well) were stimulated with r27, r27ΔSP (10 μg/ml), or LPS (5 μg/ml) for 24 h in the presence or absence of polymyxin B (5 μg/ml). After this period, [3H]thymidine was added for 16 h, and the proliferation response was measured. #, P < 0.001 (compared to stimulation with r27); *, P < 0.01 (compared to the relevant non-polymyxin B-treated group). (B) Mice were injected intravenously with 25 μg of r27, r27ΔSP, or saline as a control. Five days after the injection, spleens were removed, and total splenocytes were counted by trypan blue exclusion. **, P < 0.001 (compared to r27-injected mice).