Plasma cells (PCs) in human palatine tonsils are predominantly located in the germinal centres (GCs), in the subepithelial space and near the deep connective tissue septa surrounding each crypt. We analysed the location, phenotype, and proliferation of GC PCs by immunohistology comparing them to PCs in the other two locations. Most PCs in GCs were strongly positive for CD38, CD138, CD27, IRF4, and intracellular (ic) IgG. They often accumulated in the basal light zone, but could also be found scattered in the entire light zone. In addition, rows of PCs occurred at the surface of the GC bordering the mantle zone, i.e., in the outer zone, and at the surface of the dark zone. The latter cells were often continuous with PCs in the extrafollicular area. The vast majority of GC PCs were negative for Ki-67. Only a few Ki-67⁺ plasmablasts, predominantly icIgG⁺ or icIgM⁺, were found inside GCs. In certain GCs PCs accumulated around capillaries and the adjacent perikarya of follicular dendritic cells (FDCs). Newly formed PCs might migrate from the basal to the superficial part of the light zone and then back to the dark zone surface to leave the GC. This guarantees an even distribution of secreted Ig for exchange with immune complexes on FDCs. The surface of the dark zone may also be an exit site for Ki-67⁺CD30⁺ B lymphoblasts, which seed perifollicular and extrafollicular sites. We speculate that these cells tend to downmodulate CD20 and activation-induced deaminase and further up-regulate CD30 when developing into pre-plasmablasts.

人p扁桃体中的浆细胞（PCs）主要位于生发中心（GCs），上皮下空间以及每个隐窝周围的深结缔组织隔附近。我们通过免疫组织学分析了GC PCs的位置，表型和增殖，并将其与其他两个位置的PCs进行了比较。GC中的大多数PC均对CD38，CD138，CD27，IRF4和细胞内（ic）IgG呈强阳性。它们通常积聚在基础光区中，但也可以发现它们分散在整个光区中。另外，PC的行出现在与地幔区接壤的GC表面上，即在外部区域，以及在暗区的表面。后者的细胞通常在卵泡外区域与PC连续。绝大多数GC PC均对Ki-67阴性。只有少数Ki-67 ⁺在GC内部发现成浆细胞，主要是icIgG ⁺或icIgM ⁺。在某些GC中，PC聚集在毛囊树突状细胞（FDC）的毛细血管和邻近的核周周围。新形成的PC可能会从基底区域迁移到亮区的浅表部分，然后再迁移到暗区表面，从而离开GC。这样可以保证分泌的Ig均匀分布，以便与FDC上的免疫复合物交换。暗区的表面也可能是Ki-67 ⁺ CD30 ⁺ B淋巴母细胞的出口位点，其在卵泡周围和卵泡外位点播种。我们推测这些细胞在发育成成浆细胞前趋于下调CD20和激活诱导的脱氨酶，并进一步上调CD30。