Porgador A, Irvine K R, Iwasaki A, Barber B H, Restifo N P, Germain R N
Lymphocyte Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892-1892, USA.
J Exp Med. 1998 Sep 21;188(6):1075-82. doi: 10.1084/jem.188.6.1075.
Cutaneous gene (DNA) bombardment results in substantial expression of the encoded antigen in the epidermal layer as well as detectable expression in dendritic cells (DC) in draining lymph nodes (LNs). Under these conditions, two possible modes of DC antigen presentation to naive CD8+ T cells might exist: (a) presentation directly by gene-transfected DC trafficking to local lymph nodes, and (b) cross-presentation by untransfected DC of antigen released from or associated with transfected epidermal cells. The relative contributions of these distinct modes of antigen presentation to priming for cytotoxic T cell (CTL) responses have not been clearly established. Here we show that LN cells directly expressing the DNA-encoded antigen are rare; 24 h after five abdominal skin bombardments, the number of these cells does not exceed 50-100 cells in an individual draining LN. However, over this same time period, the total number of CD11c+ DC increases more than twofold, by an average of 20,000-30,000 DC per major draining node. This augmentation is due to gold bombardment and is independent of the presence of plasmid DNA. Most antigen-bearing cells in the LNs draining the site of DNA delivery appear to be DC and can be depleted by antibodies to an intact surface protein encoded by cotransfected DNA. This finding of predominant antigen presentation by directly transfected cells is also consistent with data from studies on cotransfection with antigen and CD86-encoding DNA, showing that priming of anti-mutant influenza nucleoprotein CTLs with a single immunization is dependent upon coexpression of the DNAs encoding nucleoprotein and B7.2 in the same cells. These observations provide insight into the relative roles of direct gene expression and cross-presentation in CD8+ T cell priming using gene gun immunization, and indicate that augmentation of direct DC gene expression may enhance such priming.
皮肤基因（DNA）轰击导致编码抗原在表皮层大量表达，并且在引流淋巴结（LN）的树突状细胞（DC）中也可检测到表达。在这些条件下，DC向初始CD8⁺T细胞呈递抗原可能存在两种模式：（a）通过基因转染的DC迁移至局部淋巴结直接呈递，以及（b）未转染的DC对从转染的表皮细胞释放或与之相关的抗原进行交叉呈递。这些不同的抗原呈递模式对细胞毒性T细胞（CTL）反应启动的相对贡献尚未明确确定。在这里我们表明，直接表达DNA编码抗原的LN细胞很少见；在腹部皮肤进行五次轰击后24小时，在单个引流LN中这些细胞的数量不超过50 - 100个。然而，在同一时间段内，CD11c⁺DC的总数增加了两倍多，每个主要引流淋巴结平均增加20,000 - 30,000个DC。这种增加是由于金轰击，并且与质粒DNA的存在无关。在DNA递送部位引流的LN中，大多数携带抗原的细胞似乎是DC，并且可以被针对共转染DNA编码的完整表面蛋白的抗体耗尽。直接转染细胞主要进行抗原呈递这一发现也与抗原和编码CD86的DNA共转染的研究数据一致，表明单次免疫引发抗突变流感核蛋白CTL依赖于在同一细胞中共表达编码核蛋白和B7.2的DNA。这些观察结果为基因枪免疫中直接基因表达和交叉呈递在CD8⁺T细胞启动中的相对作用提供了见解，并表明增强直接DC基因表达可能会增强这种启动。
