Culture of dendritic cells from a nonlymphoid organ, the thyroid gland: Evidence for TNF alpha-dependent phenotypic changes of thyroid-derived dendritic cells

Because they are sparsely distributed in tissues, dendritic cells (DC) pres ent in nonlymphoid organs are difficult to isolate. Only DC from skin and l ung have been successfully studied in culture. The objective of the present work was to investigate the possibility of isolating and culturing DC from an endocrine organ, the thyroid gland, which is particularly susceptible t o the development of autoimmune processes. The study was conducted on pig t hyroid glands to have sufficient amounts of starting material. This choice required the characterization of immunological reagents capable of recogniz ing DC markers in the pig species. Using a discontinuous trypsinization pro cedure, a DC population representing 2% to 3% of the thyroid cell suspensio n was reproducibly obtained. Isolated DC quantitatively attached to tissue culture-treated dishes and segregated from thyrocytes. DG identified as cel ls expressing major histocompatibility complex class II molecules, the mann ose receptor, and the S100 protein were found to have a high capacity to in ternalize labeled ligands, dextran, and mannosylated albumin. These cells h ad a phenotype of immature DC. Secondarily, a fraction of DC detached from culture dishes, and floating DC had low or no endocytic activity, a charact eristic of mature DG. Treatment of DC/thyrocytes cocultures with tumor necr osis factor alpha (TNF alpha) activated the transformation of immature DC i nto mature DC. These data show that DG isolated from the thyroid gland can be maintained immature or activated to undergo maturation in primary cultur e. The procedure of cell isolation and culture should be adaptable to human thyroid tissue for in vitro analyses of DG-mediated immune responses.