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.