Berthou C, Michel L, Soulié A, Jean-Louis F, Flageul B, Dubertret L, Sigaux F, Zhang Y, Sasportes M
INSERM U462, Hôpital St. Louis, Paris, France.
J Immunol. 1997 Dec 1;159(11):5293-300.
In vertebrate tissues, cell integrity is maintained by at least three mechanisms. During an immune response, injured cells are eliminated by cytotoxic lymphoid cells that produce perforin, granzyme B, and Fas ligand (FasL). Second, epithelial cells can produce FasL as an immunosuppressive protein, probably to protect the tissue against immune-mediated damage. Third, locally secreted antimicrobial peptides can be operative in the protection of animal and human epithelia. In this work, as another contribution to local mechanisms of host defense, the ability of human epidermal keratinocytes to produce cytotoxic proteins was investigated. To address this question, freshly isolated human epidermal cells and keratinocytes grown in vitro were studied. Freshly isolated epidermal cells did not express the cytolytic proteins. In contrast, keratinocyte growth to confluence was associated with granzyme B, perforin, and FasL mRNA and protein synthesis. These proteins were secreted in the culture medium. Further analysis showed that they were identical with the ones used by cytotoxic lymphocytes. Their function was then investigated with a view to a potential role in epidermal cell integrity. The data showed that activated human keratinocytes were able to protect against invading pathogens through granzyme B expression. This was demonstrated by the ability of granzyme B to greatly decrease the bacterial growth of Staphylococcus epidermidis. In addition, keratinocytes expressing FasL were found to prevent immune epidermal cell damage. Apoptosis of Fas-sensitive T cells occurred during coculture with confluent epidermal keratinocytes and was largely reduced by the addition of a FasL inhibitor. The data favor keratinocyte involvement in the regulation of dermal inflammatory responses.
在脊椎动物组织中，细胞完整性至少通过三种机制得以维持。在免疫反应期间，受损细胞会被产生穿孔素、颗粒酶B和Fas配体（FasL）的细胞毒性淋巴细胞清除。其次，上皮细胞可产生FasL作为一种免疫抑制蛋白，可能是为了保护组织免受免疫介导的损伤。第三，局部分泌的抗菌肽可在保护动物和人类上皮方面发挥作用。在这项研究中，作为对宿主防御局部机制的另一贡献，研究了人表皮角质形成细胞产生细胞毒性蛋白的能力。为解决这个问题，对新鲜分离的人表皮细胞和体外培养的角质形成细胞进行了研究。新鲜分离的表皮细胞不表达溶细胞蛋白。相比之下，角质形成细胞生长至汇合与颗粒酶B、穿孔素和FasL的mRNA及蛋白合成相关。这些蛋白分泌到培养基中。进一步分析表明，它们与细胞毒性淋巴细胞所使用的蛋白相同。随后研究了它们的功能，以探讨其在表皮细胞完整性方面的潜在作用。数据表明，活化的人角质形成细胞能够通过表达颗粒酶B来抵御入侵病原体。这通过颗粒酶B大幅降低表皮葡萄球菌细菌生长的能力得以证明。此外，发现表达FasL的角质形成细胞可防止免疫介导的表皮细胞损伤。在与汇合的表皮角质形成细胞共培养期间，Fas敏感T细胞发生凋亡，而添加FasL抑制剂可大大减少这种凋亡。这些数据支持角质形成细胞参与调节皮肤炎症反应。
