Function of Dendritic cells and their differentiation

树突状细胞已被证明起源于骨髓中的造血干细胞。然而，人们对它们的区别知之甚少。在过去的一年里，我们建立了从增殖前体细胞诱导树突状细胞的条件，并报道了GM-CSF在悬浮培养中诱导树突状细胞前体广泛生长。GM-CSF在半固体集落系统中诱导粒细胞和巨噬细胞的混合群体的形成。因此，我们询问树突状细胞是否可以从吞噬细胞常见的集落形成前体中产生。从MHC II类阴性前体细胞经GM-CSF诱导的克隆中分离细胞的实验表明，这些克隆含有大量的树突状细胞，这些标准包括高水平的MHC II类表达、细胞内抗原含量和抗原提呈细胞功能。因此，树突状细胞代表着一种独特的免疫刺激分化途径，它是由GM-CSF诱导的，但与吞噬细胞共享一个共同的MHC II类阴性前体。树突状细胞虽然有效地对几种不同的抗原敏感，但几乎没有吞噬活性。由于内吞作用是将抗原加工成呈现在MHC II类产物上的多肽的重要手段，目前尚不清楚树突状细胞如何呈递颗粒衍生的多肽。我们发现树突状细胞可以在其增殖的祖细胞发育的早期阶段内化特定的细胞。此外，当颗粒是卡介苗(BCG)生物时，分枝杆菌抗原以一种有效的方式呈递给体外和体内的T细胞。

Dendritic cells have been shown to originate from hematopoietic stem cells in the bone marrow. However, little is known about their differentiation. In the last year, we established a condition for inducing dendritic cell from proliferating precursors, and reported that GM-CSF induces the extensive growth of dendritic-cell precursors in suspension culture.GM-CSF is known to induce the formation of mixed populations of granulocytes and macrophages in semi-solid colony systems. Therefore, we asked whether dendritic cells could arise from a colony-forming precursor that is common to phagocytes. Experiments to isolate cells from colonies that are induced by GM-CSF from MHC class II-negative precursors demonstrated that the colonies contain significant numbers of dendritic cells by several criteria, such as high levels of MHC class II expression, content of intracellular antigens, and antigen-presenting-cell function. Dendritic cells, therefore, represent a distinct immunostimulatory differentiation pathway that is induced by GM-CSF but share a common MHC class II-negative precursor with phagocytes.Dendritic cells, while effective in sensitizing T cells to several different antigens, show little or no phagocytic activity. Since endocytosis is an important means whereby antigen are processed to form the peptides that are presented on MHC class II produces, it is not apparent how dendritic cells would present particle-derived peptides. We found that dendritic cells can internalize particular during an early stage in their development from proliferating progenitors. In addition, when the particles are Bacillus Calmette-Guerin (BCG) organisms, mycobacterial antigens are presented in a potent manner to T cells in vitro and in vivo.