Key Points The mesentery and omentum in mice contain various forms of lymphoid tissues. FLAgs represent a partially compartmentalized form of lymphoid aggregate. FLAgs efficiently bind B cells and high-grade B cell lymphoma. The cellular homeostasis of lymphoid tissues is determined by the continuous interactions of mobile hematopoietic cells within specialized microenvironments created by sessile stromal cells. In contrast to the lymph nodes and mucosal lymphoid tissues with well-defined entry and exit routes, the movement of leukocytes in the peritoneal cavity is largely unknown. In this study, we report that, in addition to the omental milky spots and fat-associated lymphoid clusters, in mice, the serous surface of the mesenteric adipose streaks contains lymphocyte-rich organoids comprised of a highly compacted leaf-like part connected to the adipose tissue that can also efficiently bind B cells and high-grade B cell lymphoma (diffuse large B cell lymphoma) cells. Denoted as foliate lymphoid aggregates (FLAgs), these structures show incomplete T/B segregation and a partially differentiated stromal architecture. LYVE-1–positive macrophages covering FLAgs efficiently bind i.p. injected normal B cells as well as different types of diffuse large B cell lymphoma cells. Within FLAgs, the lymphocytes compartmentalize according to their chemokine receptor pattern and subsequently migrate toward the mesenteric lymph nodes via the mesenteric lymphatic capillaries. The blood supply of FLAgs includes short vascular segments displaying peripheral lymph node addressin, and the extravasation of lymphocytes to the omental and mesenteric adipose tissues is partly mediated by L-selectin. The appearance of i.p. injected cells in mesenteric lymph nodes suggests that the mesentery-associated lymphatics may also collect leukocytes from the fat-associated lymphoid clusters and FLAgs, thus combining the mucosal and serous exit of mobile leukocytes and increasing the range of drainage sites for the peritoneal expansion of lymphoid malignancies.

中文翻译：

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叶状淋巴样聚集体作为腹膜 B 细胞和高级别 B 细胞淋巴瘤浆液性淋巴细胞进入位点的新形式

要点 小鼠的肠系膜和网膜含有多种形式的淋巴组织。FLAgs 代表淋巴聚集体的部分分隔形式。FLAgs 有效地结合 B 细胞和高级别 B 细胞淋巴瘤。淋巴组织的细胞稳态是由移动造血细胞在由固着基质细胞产生的特殊微环境中的持续相互作用决定的。与具有明确进入和退出路线的淋巴结和粘膜淋巴组织相比，白细胞在腹腔中的运动在很大程度上是未知的。在这项研究中，我们报告说，除了网膜乳斑和脂肪相关淋巴簇，在小鼠中，肠系膜脂肪条纹的浆液表面含有富含淋巴细胞的类器官，由与脂肪组织相连的高度压实的叶状部分组成，该部分还可以有效地结合 B 细胞和高级 B 细胞淋巴瘤（弥漫性大 B 细胞淋巴瘤）细胞。表示为叶状淋巴聚集体 (FLAg)，这些结构显示出不完全的 T/B 分离和部分分化的基质结构。覆盖 FLAg 的 LYVE-1 阳性巨噬细胞有效结合 ip 注射的正常 B 细胞以及不同类型的弥漫性大 B 细胞淋巴瘤细胞。在 FLAg 中，淋巴细胞根据其趋化因子受体模式进行划分，然后通过肠系膜毛细血管向肠系膜淋巴结迁移。FLAg 的血液供应包括显示外周淋巴结地址素的短血管段，淋巴细胞外渗至网膜和肠系膜脂肪组织部分由 L-选择素介导。肠系膜淋巴结中 ip 注射细胞的出现表明，肠系膜相关淋巴管也可能从脂肪相关淋巴簇和 FLAg 中收集白细胞，从而结合移动白细胞的粘膜和浆液出口，并增加了引流部位的范围。淋巴恶性肿瘤的腹膜扩张。