Fundamental study on the structure and functions of lymphoid follicles with germinal center observed in the thymuses of patients with myasthenia gravis

应用免疫组织化学方法对重症肌无力（MG）患者胸腺淋巴滤泡的发育进行了研究，重点研究了胸腺的结构和功能。卵泡由大量未成熟的B淋巴细胞和一些细长的上皮细胞组成，在免疫电镜下证实细胞质中有张力丝和桥粒。这些上皮细胞以及B淋巴细胞与L26ab发生反应。它们不存在于淋巴结的滤泡中。虽然在滤泡中证实有大量的B淋巴细胞，但在约30%的患者胸腺中只有少量携带免疫球蛋白的细胞与滤泡一起存在，其余的胸腺中缺乏，此外，在这些胸腺组织中未发现免疫球蛋白重链基因（Igh）的重排。胸腺滤泡上皮细胞在结构上与人类新生儿髓质区上皮细胞相似。MG患者胸腺组织凋亡中，与凋亡相关的Fas抗原在胸腺淋巴滤泡中表达减少，但在其余胸腺组织中表达弥漫性显著。BMI抗原在淋巴滤泡和胸腺其他部位均未表达。胸腺组织中Fas mRNA也有不同程度的降低。MG患者的胸腺瘤约有45%与髓质分化或淋巴样卵泡相关，而非MG患者的胸腺瘤中没有发现这些。B淋巴细胞集中于这些区域，但携带免疫球蛋白的细胞很少或缺乏。由此可见，MG患者胸腺滤泡或胸腺瘤中集中的B淋巴细胞表现出抗体产生的预激活状态，胸腺淋巴滤泡上皮细胞可能与抗体产生相关的免疫功能有关，淋巴滤泡中的细胞可能能够降低MG患者胸腺中T淋巴细胞的负调控。少

The developing lymphoid follicles in the thymuses of patients with myasthenia gravis (MG) were immunohistochemically investigated with emphasis on the structure and functions of the thymus.The follicles were composed of abundant immature B lymphocytes and some elongated epithelial cells in which tonofilaments and desmosomes in the cytoplasm were confirmed by an immunoelectron microscopic method. These epithelial cells as well as B lymphocytes reacted with L26ab. They were not present in the follicles of the lymphnodes. Although a significant population of B lymphocytes was confirmed in the follicle, only a few immunoglobulin-bearing cells were present in the thymuses together with the follicles at about 30 % patients and lacked in the remaining thymuses, furthermore, no rearrangement of immunoglobulin heavy chain gene (Igh) was recognized in these thymic tissues. The epithelial cells in the thymic follicles were structurally similar to those in the medullary zone of the human neonatal … More thymus.Regarding apoptosis of the thynic tissues from MG patients, expression of Fas antigen related to apoptosis was reduced in the lymphoid follicles of the thymus, but was diffusely significant in the remaining thymic tissues. BMI antigen was not expressed in the lymphoid follicles nor other parts of the thymus. Fas mRNA was also decreased to a varying degree in the thymic tissues.Thymomas of patients with MG were at about 45 % associated with medullary differentiation or lymphoid follicles that were not found in thymomas of patients without MG.B lymphocytes were concentrated in these areas, but immunolobulin-bearing cells were scarce or lacked.From these results, it was concluded that B lymphocytes concentrated in the follicles of the thymuses or thymomas from patients with MG revealed a state of preactivated antibody production, the epithelial cells in the lymphoid follicle of the thymus might be related to an immunological function associated with antibody production and the cells included in the lymphoid follicles might be able to reduce a negative regulation for T lymphocytes in the thymuses of patients with MG. Less