Morphological study on the function of antigen transporting cell (ATC) and follicular dendritic cell (FDC) in the lymph node

应用电镜和免疫组化技术对小鼠淋巴结内抗原转运细胞（ATC）和滤泡树突状细胞（FDC）进行观察.用辣根过氧化物酶（HRP）和匙孔血蓝蛋白（KLH）两种不同的抗原免疫后，仅重复注射HRP可诱导大量KLH在淋巴结内聚集，而HRP对FDC突起无作用。结论：1.位于被膜下窦内皮细胞下方的抗原转运细胞同时具有KLH和HRP.在通过MDPCl 2注射消除巨噬细胞后，MOMA- 1阳性细胞在淋巴结的被膜下窦中消失。FDC-M1阳性细胞位于被膜下窦附近和滤泡区。抗原注射后5天，在注射MDPCl 2的小鼠中呈现ATC，而没有MOMA-1阳性细胞。ATC与MOMA-1阳性细胞不同.我们研究了HRP重复注射到大鼠足垫后，腘淋巴结中FDCs上标记蛋白的表达。淋巴结生发中心（GMC）的抗原积累减少表明40次抗原刺激后FDC上的抗原交换受到抑制。在整个研究期间，S-100蛋白反应保持不变，表明FDC群体保留在GMC中。另一方面，在接受40次注射的动物中，GMC中的EDS和MRC OX-2反应降低。反复抗原刺激后，FDC表面抗原交换的减少及其表型的改变可能参与了FDC功能的调节，提示抗原反复注射后，FDC并未被破坏，但其功能可能下调。ATC和FDC对抗原的不同反应提示这两种细胞可能是不同类型的细胞。

Antigen transporting cell (ATC) and follicular dendrtic cell (FDC) in the murine lymph node were investigated by electron microscopy and immunohistochemistry.1. After the immunization with two different antigens, horseradish peroxidase (HRP) and keyhole limpet hemocyanin (KLH), only HRP repeated injection induced the accumulation of large number of KLH, but no HRP on the processes of FDC in the lymph nodes. Antigen transporting cells (ATCs) located beneath the endothelial cells in the subcapsular sinus possessed both KLH and HRP.2. After elimination of the macrophages by MDPCl2 injections, MOMA- 1 positive cells disappeared in the subcapsular sinus in the lymph node. FDC-M1 positive cells remained near the subcapsular sinus and in the follicular area. Five days after the antigen injection, ATCs were presented in the MDPCl2 injected mice without MOMA-1 positive cells. ATC is different from the MOMA-1 positive cells.3. We investigated the expression of marker proteins on FDCs in popliteal lymph nodes after repeated injections of HRP into the rat footpads. The decreased accumulation of antigens in the germinal center (GMC) of lymph nodes indicated suppressed antigen exchange on FDCs after 40 antigen stimulations. S-100 protein reactions remained unchanged throughout the study, suggesting that the FDC population was preserved in GMC. On the other hand, EDS and MRC OX-2 reactions in GMC were decreased in animals given 40 injections. Decreased antigen exchange on FDC and its altered phenotype may play a role in the regulation of FDC function after repeated antigen stimuli.These experiments suggested that after antigen repeated injection, FDC was not destroyed, but may down regulate in the function. The different reaction of ATC and FDC for the antigens suggests these cells may be different type of cells.