Ogimoto M, Katagiri T, Hasegawa K, Mizuno K, Yakura H
Tokyo Metropolitan Institute for Neuroscience, Japan.
Cell Immunol. 1993 Oct 1;151(1):97-109. doi: 10.1006/cimm.1993.1224.
In this study, we examined whether CD45 isoform can be switched in murine mature B cells and what signals are responsible for the process. Stimulation of murine splenic B cells with lipopolysaccharide did not reduce the expression of CD45RA-, B-, and C-exon-dependent epitopes or a CD45 common epitope, but rather enhanced the expression. Stimulation with goat antimouse IgM antibody did not significantly reduce CD45 expression but caused a partial reduction in the expression of CD45RA-, B-, and C-exon-dependent epitopes. Phorbol myristate acetate (PMA) alone did not significantly alter the expression of CD45 but the combination of PMA and ionomycin induced a strong reduction in the expression of CD45RA-, B-, and C-exon-dependent epitopes without affecting the level of CD45 common epitope expression. Reverse transcription and polymerase chain reaction analysis demonstrated that CD45 isoform switch induced by anti-IgM or PMA plus ionomycin is indeed mediated by alternative splicing of A-, B-, and C-exon-derived mRNA. These results suggest that CD45 isoform of murine mature B cells can be switched by antigen receptor-mediated signals, and the process seems to be regulated at least in part by protein kinase C activation and mobilization of calcium ions.
在本研究中，我们检测了小鼠成熟B细胞中CD45异构体是否能够转换以及哪些信号负责这一过程。用脂多糖刺激小鼠脾B细胞并未降低CD45RA、B和C外显子依赖性表位或CD45共同表位的表达，反而增强了表达。用山羊抗小鼠IgM抗体刺激并未显著降低CD45表达，但导致CD45RA、B和C外显子依赖性表位的表达部分降低。单独使用佛波醇肉豆蔻酸酯乙酸盐（PMA）并未显著改变CD45的表达，但PMA与离子霉素联合使用可强烈降低CD45RA、B和C外显子依赖性表位的表达，而不影响CD45共同表位的表达水平。逆转录和聚合酶链反应分析表明，抗IgM或PMA加离子霉素诱导的CD45异构体转换确实是由A、B和C外显子来源的mRNA的可变剪接介导的。这些结果表明，小鼠成熟B细胞的CD45异构体可通过抗原受体介导的信号进行转换，并且该过程似乎至少部分受蛋白激酶C激活和钙离子动员的调节。
