Localization of macrophages and dendritic cells in human thoracic lymph nodes: An immunohistochemical study using surgically obtained specimens

Both dendritic cells (DCs) and macrophages are bone marrow‐derived cells that perform antigen presentation. The distribution of DCs and CD68‐positive macrophages were immunohistochemically examined in 103 thoracic nodes obtained from 23 lung cancer patients (50–84 years old) without metastasis. Among three antibodies tested initially—CD209/DCsign, fascin, and CD83—DCsign was chosen as the DC marker. For comparison, 137 nodes from 12 patients with cancer metastasis were also examined histologically. In patients without metastasis, DCs were found as (1) clusters along the subcapsular sinus and in a border area between the medullary sinus and cortex (mean sectional area of multiple nodes at one site, 8.4%) and, (2) rosette‐like structures in the cortex (mean number in multiple nodes at one site, 20.5). Notably, DC clusters and rosettes contained no or few macrophages and were surrounded by smooth muscle actin (SMA)‐positive, endothelium‐like cells. The subcapsular linear cluster corresponded to 5%–85% (mean, 34.0%) of the nodal circumferential length and was shorter in older patients (p = 0.009). DC rosettes, solitary, or communicating with a cluster, were usually connected to a paracortical lymph sinus. Few differences were found between nodes with or without metastasis, but DC cluster sometimes contained abundant macrophages in cancer metastasis patients. The subcapsular DC cluster is not known in the rodent model, in which the subcapsular sinus is filled with macrophages. This quite different, even complementary, distribution suggests no, or less, cooperation between DCs and macrophages in humans. Dendritic cell (DC) clusters and rosettes contained no or few macrophages and were surrounded by smooth muscle actin‐positive, endothelium‐like cells. Few differences between nodes with or without metastasis, but DC cluster sometimes contained abundant macrophages in cancer metastasis patients.