Are dendritic cells in smoking induced lung diseases functionally impaired?

Introduction: Dendritic cells (DC) present antigens for an immune reaction. Subtypes of DC such as plasmocytic (pDC), monocytoid (mDC), immature (imDC), classical (cDC), follicular (fDC), and interdigitating (intDC) and Langerhans cells (LHC) either aggravate or limit an immune reaction. Not much is known about the role of LHC and DCs in respiratory bronchiolitis-interstitial lung disease (RB-ILD), and desquamative interstitial pneumonia (DIP) and Langerhans cell histiocytosis (LHCH). Material and Methods: 20 cases of RB-ILD, 7 cases of DIP, and 14 cases of LHCH were investigated. All patients were excessive cigarette smokers. Gender distribution showed a higher incidence of males. Immunohistochemistry was performed using antibodies for S100 protein, HLA-DR, CD11b, CD11c, CD14, CD15, CD33, CD35, CD64, CD123, CD303, and CD207. Results and Conclusion: LHC were enriched in LHCH, and increased in RB-ILD, whereas absent in DIP. cDC were more frequent in LHCH compared to RB-ILD and DIP, whereas mDC were equally found in all three diseases. intDC and imDC were increased in LHCH compared to RB-ILD and DIP. Accumulation of imDC and pDC could be a sign of impaired maturation. Tertiary lymph follicles seen in RB-ILD and LHCH, but absent in DIP, were populated by fDC, other DCs were absent, again pointing to an impaired immune reaction. Follicle centers were seen in RB-ILD but absent in LHCH. pDC were equally seen in LHCH and RB-ILD, but absent in DIP. RB-ILD despite similarities with DIP is a different entity with different subsets of DCs.