TxA₂-TP axis participates in the early B-cell development. (A) Prostanoid profiles in purified B-cell subpopulations from BM were examined by mass spectrum assays. Results show the mean ± SEM of 6 independent experiments. (B) mRNA expression of receptors for prostanoids in purified B cells was evaluated by semiquantitative RT-PCR. Data are representative of 4 independent experiments. (C) mRNA expression of TP in distinct stages of developing B cells derived from BM of naïve mice was evaluated by RT-PCR. We used β-actin for normalization, and the group with lowest expression was artificially set as 1. Results show the mean ± SEM of 3 independent experiments from 3 mice. (D) Flow cytometric analysis of distinct B-cell populations in BM from TP^−/− and WT controls (n = 6). (E) BM transplantation experiments: BM cells from TP^−/− or WT mice (CD45.2⁺) were mixed with BM from syngenic mice (CD45.1⁺) at a 1:1 ratio, and cells were then injected into irradiated syngenic mice (n = 6). The percentages of distinct B-cell compartments among CD45.2⁺ cells in BM were analyzed 6 weeks after transplantation. (F) The relative WT/KO ratios of B-cell subpopulations in E were normalized against pre-pro-B cells. Mean ± SEM from 6 mice is shown. (D-E) (Upper) Representative results from 1 single experiment; numbers adjacent indicate percentages of total living cells. (Lower) Mean ± SEM from all mice analyzed. *P < .05 and **P < .01, using unpaired Student t tests.