Regulation of Dendritic Cell Function by Surfactant Protein D

Abstract

RATIONALE: Surfactant protein-D (SP-D) plays an important protective role and may modulate dendritic cells (DC) in the lung. How SP-D affects pulmonary DC function is unclear.METHODS: Expression of the DC-associated chemokines and their receptors Ccl17 (TARC), 19 and 21, Ccr4 and 7 was analyzed by real-time PCR, ELISA and flow cytometry in lungs and thoracic lymph nodes of conditional SP-D expressor and SP-D-/- mice sensitized and challenged with the allergen Aspergillus fumigatus (Af). The direct effect of SP-D on DC maturation from bone marrow derived progenitor cells was analyzed in vitro by immunocytochemistry and flow cytometry.RESULTS: SP-D-/- mice showed accumulation of lymphocytes in the airway submucosal tissue and had a nearly 10-fold higher expression of Ccl17 and its receptor, Ccr4, than SP-D+/+ mice, suggesting local activation of Th2 cells. Indeed, expression of Ccr7, the receptor responsible for facilitating migration of lung DC to the thoracic lymph nodes, was significantly reduced in the lung tissue of SP-D-/- mice following intranasal challenge of sensitized mice with Af. Concurrent inhalation of a fluorescein label (CFSE) revealed that allergen uptake did not induce retrograde migration of DC in the lung of SP-D-/- mice: The number of CD11c+/CFSE+ cells recovered from the thoracic lymph nodes of these mice was significantly reduced in comparison with SP-D+/+ mice.CONCLUSIONS: Since SP-D markedly inhibited expression of CD86 and MHC-II in vitro, we conclude that presence of this innate immune molecule is essential for compartmentalization of the immune response to the lymph nodes. RATIONALE: Surfactant protein-D (SP-D) plays an important protective role and may modulate dendritic cells (DC) in the lung. How SP-D affects pulmonary DC function is unclear. METHODS: Expression of the DC-associated chemokines and their receptors Ccl17 (TARC), 19 and 21, Ccr4 and 7 was analyzed by real-time PCR, ELISA and flow cytometry in lungs and thoracic lymph nodes of conditional SP-D expressor and SP-D-/- mice sensitized and challenged with the allergen Aspergillus fumigatus (Af). The direct effect of SP-D on DC maturation from bone marrow derived progenitor cells was analyzed in vitro by immunocytochemistry and flow cytometry. RESULTS: SP-D-/- mice showed accumulation of lymphocytes in the airway submucosal tissue and had a nearly 10-fold higher expression of Ccl17 and its receptor, Ccr4, than SP-D+/+ mice, suggesting local activation of Th2 cells. Indeed, expression of Ccr7, the receptor responsible for facilitating migration of lung DC to the thoracic lymph nodes, was significantly reduced in the lung tissue of SP-D-/- mice following intranasal challenge of sensitized mice with Af. Concurrent inhalation of a fluorescein label (CFSE) revealed that allergen uptake did not induce retrograde migration of DC in the lung of SP-D-/- mice: The number of CD11c+/CFSE+ cells recovered from the thoracic lymph nodes of these mice was significantly reduced in comparison with SP-D+/+ mice. CONCLUSIONS: Since SP-D markedly inhibited expression of CD86 and MHC-II in vitro, we conclude that presence of this innate immune molecule is essential for compartmentalization of the immune response to the lymph nodes.