Lin T J, Hirji N, Nohara O, Stenton G R, Gilchrist M, Befus A D
Pulmonary Research Group, Department of Medicine, University of Alberta, Edmonton, Canada.
J Immunol. 1998 Dec 1;161(11):6265-72.
CD8, a marker largely restricted to subsets of T lymphocytes and NK cells, was detected on freshly isolated rat peritoneal mast cells (PMC). Using flow cytometry, Percoll-enriched rat PMC (> or = 98% purity) were positive for the hinge region of CD8alpha (67.5 +/- 9.5%; Ab OX8) and CD8beta (27.8 +/- 2.3%; Ab 341). CD8+ PMC consisted of two populations, CD8alpha+ (22.5%) and CD8alpha+ beta+ (15.9%). Interestingly, G28, an Ab that identifies the IgV-like region of CD8alpha on T lymphocytes, did not bind PMC, suggesting that PMC CD8alpha is distinct from that on T lymphocytes. Moreover, a similar pattern of Ab positivity for CD8 was observed on a rat mast cell line, RBL 2H3. The presence of CD8alpha immunoreactivity on rat PMC was further confirmed by confocal microscopy. In situ reverse-transcription PCR and reverse-transcription PCR analysis demonstrated that PMC contained mRNA transcripts encoding CD8alpha. In functional studies of CD8 on PMC, both TNF-alpha and nitric oxide production were induced by OX8 (CD8alpha) and 341 Ab (CD8beta) in a dose-dependent manner. However, neither OX8 nor 341 induced histamine secretion from PMC. Ag-induced secretion of TNF-alpha, nitric oxide, and histamine was not affected by OX8 or 341 Abs, suggesting that there are distinct signaling mechanisms mediated by CD8 and Fc epsilonRI. These results indicate that rat PMC express functional CD8 molecules that may be distinct from those of T lymphocytes. The difference suggests there is a ligand other than MHC class I for mast cell CD8.
CD8是一种主要局限于T淋巴细胞和自然杀伤细胞亚群的标志物，在新鲜分离的大鼠腹膜肥大细胞（PMC）中被检测到。使用流式细胞术，经Percoll富集的大鼠PMC（纯度≥98%）对CD8α铰链区（67.5±9.5%；抗体OX8）和CD8β铰链区（27.8±2.3%；抗体341）呈阳性。CD8⁺ PMC由两个群体组成，即CD8α⁺（22.5%）和CD8α⁺β⁺（15.9%）。有趣的是，识别T淋巴细胞上CD8α IgV样区域的抗体G28不与PMC结合，这表明PMC上的CD8α与T淋巴细胞上的不同。此外，在大鼠肥大细胞系RBL 2H3上也观察到了类似的CD8抗体阳性模式。共聚焦显微镜进一步证实了大鼠PMC上存在CD8α免疫反应性。原位逆转录PCR和逆转录PCR分析表明，PMC含有编码CD8α的mRNA转录本。在对PMC上CD8的功能研究中，OX8（CD8α）和341抗体（CD8β）均以剂量依赖方式诱导肿瘤坏死因子-α（TNF-α）和一氧化氮的产生。然而，OX8和341均未诱导PMC分泌组胺。抗原诱导的TNF-α、一氧化氮和组胺分泌不受OX8或341抗体的影响，这表明CD8和FcεRI介导不同的信号传导机制。这些结果表明，大鼠PMC表达功能性CD8分子，可能与T淋巴细胞的不同。这种差异表明肥大细胞CD8存在除MHC I类分子以外的配体。
