Résumé
Hypersensitivity pneumonitis (HP) is an inflammatory lung disease characterized by a chronic T cell airway infiltration. Dendritic cells (DC) have been reported to play a crucial role in trafficking of antigen to the lymph nodes and antigen presentation in this disease. However, little is know about what triggers and mediates DC trafficking in HP. CD34 is a sialomucin best known for it's expression on hematopoietic progenitors. This protein, which was recently reported as a facilitator of cell trafficking, is also expressed on a few subsets of mature cells such as DCs. We therefore explored whether CD34 expression in DCs was involved in DC trafficking to and from the lung in a mouse model of HP, using wild type and Cd34-/- mice. Lung inflammation and DC recruitment was evaluated in both strains. Results show that lack of CD34 expression leads to a lower lung inflammation (as characterized by lower total cell counts in the broncho-alveolar lavage). DC recruitment was reduced in the alveoli of Cd34-/- mice, but was increased in the lung tissue. Using bone marrow chimeric mice, this effect was attributed to the Cd34-/- environment (including potentially radio-resistant DCs). Lastly, intraveinous injection of wild type DCs reconstituted disease in Cd34-/- mice. We conclude that CD34 could mediate DC trafficking in HP and possibly other inflammatory lung diseases. Supported by the Canadian Institutes of Health Research (CIHR), AllerGen Network Centre of Excellence (KMM), Multiple Sclerosis Society of Canada (JLB), Michael Smith Foundation for Health Research (KMM, MRB), and FRSQ (MRB)