A Discrete Subpopulation of Dendritic Cells Transports Apoptotic Intestinal Epithelial Cells to T Cell Areas of Mesenteric Lymph Nodes

This study identifies a dendritic cell (DC) subset that constitutively transports apoptotic intestinal epithelial cell remnants to T cell areas of mesenteric lymph nodes in vivo. Rat intestinal lymph contains two DC populations. Both populations have typical DC morphology, are major histocompatibility complex class II(hi), and express OX62, CD11c, and B7. CD4(+)/OX41(+) DCs are strong antigen-presenting cells (APCs). CD4(−)/OX41(−) DCs are weak APCs and contain cytoplasmic apoptotic DNA, epithelial cell–restricted cytokeratins, and nonspecific esterase (NSE)(+) inclusions, not seen in OX41(+) DCs. Identical patterns of NSE electrophoretic variants exist in CD4(−)/OX41(−) DCs, intestinal epithelial cells, and mesenteric node DCs but not in other DC populations, macrophages, or tissues. Terminal deoxynucleotidyl transferase–mediated dUTP-biotin nick-end labeling (TUNEL)-positive DCs and strongly NSE(+) DCs are present in intestinal lamina propria. Peyer's patches and mesenteric but not other lymph nodes contain many strongly NSE(+) DCs in interfollicular and T cell areas. Similar DCs are seen in the ileum and in T cell areas of mesenteric nodes in gnotobiotic rats. These results show that a distinct DC subset constitutively endocytoses and transports apoptotic cells to T cell areas and suggest a role for these DCs in inducing and maintaining peripheral self-tolerance.