{'fraction_non_alphanumeric': 0.03875, 'fraction_numerical': 0.015625, 'mean_word_length': 5.783898305084746, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Ontogenic development of macrophage subpopulations and la‐positive dendritic cells in fetal and neonatal rat spleen

Development, differentiation, and distribution of macrophage subpopulations and la+ dendritic cells in the fetal and neonatal rat spleen were investigated by means of double immunohistochemical staining and im‐ munoelectron microscopy. To characterize these cell populations, a panel of anti‐rat macrophage monoclonal antibodies (RM‐1, ED2, ED3, TRPM‐3, Ki‐M2R) and an anti‐rat la antibody (OX6) were used. In the fetal rat spleen, macrophages were first detected by RM‐1 at fetal day 15. ED2+ and/or Ki‐M2R+ macrophages appeared at fetal day 16. TRPM‐3+ and/or ED3+ macrophages appeared a day later. During the fetal and neonatal development, ED2+ and TRPM‐3+ macrophages differentiated independently, maturing into red pulp macrophages and marginal metallophilic and marginal zone macrophages respectively. Intimate topographical relations were observed between ED2+ macrophages and hematopoietic cells and between TRPM‐3+ macrophages and marginal zone lymphocytes. Ia+ cells were first observed around arterioles at fetal day 15. In the fetal and neonatal period, the number of la+ cells gradually increased, their shape became dendritic, and they matured into interdigitating cells in the inner periarteriolar lymphatic sheath. In ontogeny, la+ dendritic cells were not stained with ED2 or TRPM‐3. These results suggest that ED2+ macrophages, TRPM‐3+ macrophages, and Ia+ dendritic cells are distinct cell lines that pursue independent developmental processes in spleen ontogeny.