Dong Q, Wright J R
Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
J Immunol. 1996 Jun 15;156(12):4815-20.
C-reactive protein (CRP) is well characterized as one of the serum acute phase proteins, the levels of which increase dramatically after infection. CRP has been shown to be involved in multiple immunoregulatory functions. For example, it activates the classical complement cascade, opsonizes bacteria for phagocytosis, and stimulates phagocytic cells. Although CRP is predominantly produced and secreted by hepatocytes, other cells including subsets of lymphocytes, Kupffer cells, and blood monocytes have been shown to synthesize this protein as well. We hypothesized that CRP may be produced in the lung, and therefore it could function directly in pulmonary host defense. Western blot analysis showed that CRP was present in the lung tissue, lung lavage, and alveolar macrophages. This result was further confirmed by immunohistochemical staining of lung sections that showed the localization of CRP in alveolar macrophages. The CRP mRNA was detected subsequently by reverse-transcriptase PCR (RT-PCR), and a single amplified product was obtained from alveolar macrophages as well as from whole lung tissue. Both were the same size as the amplified product obtained from liver mRNA. Furthermore, in situ hybridization with CRP riboprobe demonstrated specific staining of alveolar macrophages both in lung sections and isolated cells. In addition, in situ hybridization showed that CRP mRNA levels in isolated alveolar macrophages were up-regulated by in vitro LPS stimulation. In summary, these results indicate that CRP is produced by alveolar macrophages, and suggest that CRP may be involved in the pulmonary immune response.
C反应蛋白（CRP）作为血清急性期蛋白之一已得到充分表征，其水平在感染后会急剧升高。CRP已被证明参与多种免疫调节功能。例如，它可激活经典补体级联反应，调理细菌以便吞噬，并刺激吞噬细胞。尽管CRP主要由肝细胞产生和分泌，但包括淋巴细胞亚群、库普弗细胞和血液单核细胞在内的其他细胞也已被证明能合成这种蛋白质。我们推测CRP可能在肺中产生，因此它可能直接在肺部宿主防御中发挥作用。蛋白质印迹分析表明，CRP存在于肺组织、肺灌洗液和肺泡巨噬细胞中。肺切片的免疫组织化学染色进一步证实了这一结果，该染色显示CRP定位于肺泡巨噬细胞中。随后通过逆转录聚合酶链反应（RT-PCR）检测到了CRP mRNA，并且从肺泡巨噬细胞以及整个肺组织中均获得了单一扩增产物。两者的大小与从肝脏mRNA获得的扩增产物相同。此外，用CRP核糖探针进行的原位杂交在肺切片和分离细胞中均显示出肺泡巨噬细胞有特异性染色。另外，原位杂交显示，体外脂多糖刺激可使分离的肺泡巨噬细胞中的CRP mRNA水平上调。总之，这些结果表明CRP由肺泡巨噬细胞产生，并提示CRP可能参与肺部免疫反应。
