Schrader C E, George A, Kerlin R L, Cebra J J
Department of Biology, University of Pennsylvania, Philadelphia 19104-6018.
Int Immunol. 1990;2(6):563-70. doi: 10.1093/intimm/2.6.563.
Microcultures of helper T (Th) cells and a few appropriately primed murine B cells can be used to detect cognate T-B interactions which lead to clonal production of IgM, IgG1, and IgE. However, IgG2, IgG3, and IgA are very rarely expressed. We have found that the addition of dendritic cells to such cultures creates an extremely supportive environment for clones expressing IgA with other isotypes, as well as clones expressing only detectable IgA. Typically, 400 dendritic cells were added to 3000 conalbumin-specific Th cells (D10.G4.1) and 30 hapten-specific Peyer's patch (PP) B cells with antigen in 15 microliters. The response was antigen dependent and clonal. Almost half of the clones expressed only non-IgM isotypes, 43% expressed some IgA, and 14% expressed some IgG3; isotype diversity increased over time. Dendritic cells from PP and spleen were found to be equally supportive, and allowed the number of T cells required in microculture to be decreased from 3000 to 400. However, T cell proliferation was not required for the supportive effect of dendritic cells. Surface IgD-bearing cells were also found to switch to IgA production in microculture as judged by their generating clones expressing IgM along with IgA and other isotypes. Again, IgA was usually expressed only in the presence of dendritic cells. The mechanism may involve dendritic cell-induced T cell activation and/or dendritic cell factors, and is under investigation.
辅助性T（Th）细胞的微培养物和一些经过适当致敏的小鼠B细胞可用于检测同源T-B相互作用，这种相互作用会导致IgM、IgG1和IgE的克隆性产生。然而，IgG2、IgG3和IgA很少表达。我们发现，在此类培养物中添加树突状细胞可为表达IgA及其他同种型的克隆以及仅表达可检测到的IgA克隆创造一个极其有利的环境。通常，将400个树突状细胞添加到含有抗原的15微升中，其中有3000个伴清蛋白特异性Th细胞（D10.G4.1）和30个半抗原特异性派尔集合淋巴结（PP）B细胞。该反应是抗原依赖性的且具有克隆性。几乎一半的克隆仅表达非IgM同种型，43%表达一些IgA，14%表达一些IgG3；同种型多样性随时间增加。发现来自PP和脾脏的树突状细胞具有同样的支持作用，并使微培养所需的T细胞数量从3000减少到400。然而，树突状细胞的支持作用并不需要T细胞增殖。通过其产生同时表达IgM以及IgA和其他同种型的克隆判断，还发现表面带有IgD的细胞在微培养中会转换为产生IgA。同样，IgA通常仅在有树突状细胞存在时才表达。其机制可能涉及树突状细胞诱导的T细胞活化和/或树突状细胞因子，目前正在研究中。
