Читать книгу Pathology of Genetically Engineered and Other Mutant Mice - Группа авторов - Страница 121

Milky spots are collections of leukocytes located just beneath the mesothelium in the omentum [58]. They are predominantly composed of macrophages and B1 B cells with fewer classical B2 B cells. They contain few T cells and lack a distinct T cell area that is present in other secondary lymphoid organs. Furthermore, follicular dendritic cells are absent from milky spots. Lymphoid structures similar to milky spots are found in pericardial, mediastinal, and mesenteric fat, and these are known as fat‐associated lymphoid clusters (FALCs) [59]. The formation of milky spots and FALCs requires LTA and CXCL13, but is independent of lymphoid tissue‐inducer cells. The number and size of milky spots and FALCs is increased by exposure to microbiota, suggesting that these tissues have features in common with both secondary and tertiary lymphoid tissues. Milky spots lack afferent lymphatics, and antigens enter via fenestrations in the overlying mesothelium. Inflammation and infections in the peritoneal cavity lead to a rapid increase of the number and size of milky spots as a result of an influx of peritoneal macrophages and recruitment of cells from the blood circulation. Immune responses can involve both B1 cells which differentiate into IgM and IgA‐secreting plasma cells and conventional B and T cells.