Svensson M, Stockinger B, Wick M J
Department of Cell and Molecular Biology, Lund University, Sweden.
J Immunol. 1997 May 1;158(9):4229-36.
Dendritic cells can engulf particulate Ags and induce T cell proliferative responses after pulsing with particulate Ag. However, their capacity to process viable Gram-negative bacteria for presentation by MHC-I and MHC-II has not been shown. We therefore characterized the ability of murine bone marrow-derived dendritic cells to process Escherichia coli and Salmonella typhimurium, expressing defined epitopes for presentation by MHC-I and MHC-II molecules. The I-Ak-restricted 46-61 epitope from hen egg white lysozyme (HEL(46-61)) or the Kb-restricted 257-264 epitope from chicken egg OVA (OVA(257-264)) was expressed as fusion proteins in the bacterial cytoplasm as the Crl-HEL and Crl-OVA fusion proteins, respectively. Bacteria expressing Crl-HEL or Crl-OVA, or beads coated with HEL or OVA, were coincubated with murine bone marrow-derived dendritic cells, and Ag processing and presentation were quantitated using T cell hybridomas. The data show that granulocyte-macrophage CSF-stimulated dendritic cells can process live intact Gram-negative bacteria for peptide presentation by MHC-I and MHC-II. Cytochalasin D inhibition studies revealed that processing for both MHC-I and MHC-II presentation required cytoskeletal rearrangements. Processing for MHC-I and MHC-II presentation was inhibited by ammonium chloride, suggesting that acidic compartments were required. Thus, granulocyte-macrophage CSF-stimulated murine bone marrow dendritic cells are capable of processing exogenous particulate Ags, including bacteria with no known mechanism for phagosomal escape, for peptide presentation by both MHC-I and MHC-II. These data suggest that dendritic cells may be important in priming both CD4+ and CD8+ T cells to bacterial Ags.
树突状细胞能够吞噬颗粒性抗原，并在与颗粒性抗原脉冲处理后诱导T细胞增殖反应。然而，它们处理活的革兰氏阴性菌以供MHC-I和MHC-II呈递的能力尚未得到证实。因此，我们对小鼠骨髓来源的树突状细胞处理大肠杆菌和鼠伤寒沙门氏菌的能力进行了表征，这些细菌表达特定表位以供MHC-I和MHC-II分子呈递。来自鸡卵清溶菌酶的I-Ak限制性46-61表位（HEL(46-61)）或来自鸡卵OVA的Kb限制性257-264表位（OVA(257-264)）分别作为Crl-HEL和Crl-OVA融合蛋白在细菌细胞质中表达为融合蛋白。表达Crl-HEL或Crl-OVA的细菌，或包被有HEL或OVA的珠子，与小鼠骨髓来源的树突状细胞共同孵育，并使用T细胞杂交瘤对抗原处理和呈递进行定量分析。数据表明，粒细胞-巨噬细胞集落刺激因子刺激的树突状细胞能够处理完整的活革兰氏阴性菌，以供MHC-I和MHC-II呈递肽段。细胞松弛素D抑制研究表明，MHC-I和MHC-II呈递的处理都需要细胞骨架重排。氯化铵抑制了MHC-I和MHC-II呈递的处理，表明需要酸性区室。因此，粒细胞-巨噬细胞集落刺激因子刺激的小鼠骨髓树突状细胞能够处理外源性颗粒性抗原，包括没有已知吞噬体逃逸机制的细菌，以供MHC-I和MHC-II呈递肽段。这些数据表明，树突状细胞在启动CD4+和CD8+ T细胞对细菌抗原的反应中可能很重要。
