Effects of leukotriene biosynthesis inhibitors on CD40L-induced thymidine incorporation in B-CLL cells. B-CLL cells (4 × 10⁵) were cultivated together with either irradiated L cells alone (L) or irradiated CD40L-L cells plus indicated compound(s) for 96 hours. When inhibitors and/or LTB₄ were used, B-CLL cells were pretreated with the indicated compound(s) for 30 minutes in a serum-free medium. ³H-thymidine (0.037 MBq [1 μCi]) was present for the final 8 hours of the incubation period. (A) MK-886 (1 μM-1 nM) or (B) BWA4C (100 nM-1 nM) with or without LTB₄ (150 nM). Control represents B-CLL cells cultured together with irradiated CD40L-L cells alone. Activation of B-CLL cells with CD40L-L treatment led to between 3580 and 15 369 cpm (³H-thymidine) incorporation in the different experiments (control). This was set as 100% in each experiment. Each sample was represented by triplicates. The results show the mean ± SDs from 8 separate experiments (B-CLL cells from 2 patients were analyzed 2 times). The highest concentration of MK-886 (1 μM) was only used in 3 experiments. Student t test was used to calculate statistics (ie, control vs control plus indicated compound(s) [^**P < .01, ^***P < .001]).