Migration patterns of dendritic cells in the mouse. Homing to T cell-dependent areas of spleen, and binding within marginal zone.

Abstract

Using quantitative techniques we have shown elsewhere that dendritic cells (DC) migrate from blood into the spleen, under the control of T cells. Here we traced the localization of DC within the spleen and sought to explain the means by which they entered. DC were labeled with a fluorochrome, Hoescht 33342, and injected intravenously. Spleens were removed 3 or 24 h later and DC were visualized within particular areas that were defined by mAbs and FITC anti-Igs. At 3 h most DC were in the red pulp, whereas by 24 h the majority had homed to T-dependent areas of the white pulp and may have become interdigitating cells. Lymphoid DC, isolated from spleen and perhaps normally present in blood, may thus be a migratory stage distinct from the relatively fixed interdigitating cells. We also developed a frozen section assay to investigate the interaction of DC with various lymphoid elements. When DC were incubated on sections of spleen, at 37 degrees C but not at 4 degrees C they attached specifically within the marginal zone and did not bind to T areas; in contrast, macrophages attached only to red pulp and T cells did not bind specifically. However, DC did not bind to sections of mesenteric lymph node, whereas T cells localized in particular regions at 4 degrees C but not at 37 degrees C, probably the high endothelial venules. DC may thus express "homing receptors," similar to those of T cells, for certain endothelia. We propose that T cells can modify the vascular endothelium in certain areas to allow egress of DC from the bloodstream.