Bayles Ian, Milcarek Christine
Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15261.
Crit Rev Immunol. 2014;34(6):481-99. doi: 10.1615/critrevimmunol.2014012168.
B cells can be activated by cognate antigen, anti-B-cell receptor antibody, complement receptors, or polyclonal stimulators like lipopolysaccharide; the overall result is a large shift in RNA processing to the secretory-specific form of immunoglobulin (Ig) heavy chain mRNA and an upregulation of Igh mRNA amounts. Associated with this shift is the large-scale induction of Ig protein synthesis and the unfolded protein response to accommodate the massive quantity of secretory Ig that results. Stimulation to secretion also produces major structural accommodations and stress, with extensive generation of endoplasmic reticulum and Golgi as part of the cellular architecture. Reactive oxygen species can lead to either activation or apoptosis based on context and the high or low oxygen tension surrounding the cells. Transcription elongation factor ELL2 plays an important role in the induction of Ig secretory mRNA production, the unfolded protein response, and gene expression during hypoxia. After antigen stimulation, activated B cells from either the marginal zones or follicles can produce short-lived antibody secreting cells; it is not clear whether cells from both locations can become long-lived plasma cells. Autophagy is necessary for plasma cell long-term survival through the elimination of some of the accumulated damage to the ER from producing so much protein. Survival signals from the bone marrow stromal cells also contribute to plasma cell longevity, with BCMA serving a potentially unique survival role. Integrating the various information pathways converging on the plasma cell is crucial to the development of their long-lived, productive immune response.
B细胞可被同源抗原、抗B细胞受体抗体、补体受体或脂多糖等多克隆刺激剂激活;总体结果是RNA加工发生重大转变,转向免疫球蛋白(Ig)重链mRNA的分泌特异性形式,且Igh mRNA量上调。与此转变相关的是Ig蛋白合成的大规模诱导以及未折叠蛋白反应,以适应由此产生的大量分泌性Ig。分泌刺激还会产生主要的结构适应性变化和应激,作为细胞结构的一部分,内质网和高尔基体大量生成。活性氧根据细胞周围的环境以及高氧或低氧张力,可导致激活或凋亡。转录延伸因子ELL2在缺氧期间Ig分泌性mRNA产生的诱导、未折叠蛋白反应和基因表达中起重要作用。抗原刺激后,来自边缘区或滤泡的活化B细胞可产生短命的抗体分泌细胞;尚不清楚来自这两个位置的细胞是否都能成为长寿浆细胞。自噬对于浆细胞的长期存活是必要的,它可消除因产生大量蛋白质而在内质网中积累的一些损伤。骨髓基质细胞的存活信号也有助于浆细胞的长寿,其中BCMA发挥着潜在的独特存活作用。整合汇聚到浆细胞的各种信息通路对于其长寿、高效免疫反应的发展至关重要。