Langerhans-like dendritic cells generated from cord blood progenitors internalize pollen allergens by macropinocytosis, and part of the molecules are processed and can activate autologous naive T lymphocytes.
BACKGROUND
The safety and efficacy of sublingual immunotherapy have been demonstrated in moderate allergic asthma and seasonal rhinitis. However, not much is known about the precise mechanism of action of the allergen when it crosses the oral mucosa.


OBJECTIVE
To define this mechanism, we investigated the role of Langerhans' cells in the capture and internalization of allergens.


METHODS
We generated dendritic cells in vitro with the phenotypic characteristics of Langerhans-like dendritic cells (LLDCs) from cord blood CD34(+) progenitors. We used two recombinant major allergens: Bet v 1 and Phl p 1 labeled with FITC.


RESULTS
Internalization of allergens and control proteins was dose- and time-dependent and related to the immature state of the cells. LLDCs internalized allergens with a high efficiency in comparison with control molecules. Allergens were only internalized by macropinocytosis, as demonstrated by the use of various inhibitors. Addition of intracellular pH-modifying molecules indicated that only a part of the allergens was accumulated in acidic vesicles, whereas the majority remained in other cytoplasmic structures. Pulse-chase experiments calculated a half-life of 4 hours, suggesting that part of the molecules were not metabolized in the lysosome. Allergen internalization by LLDCs might be followed by processing in some experiments, as demonstrated by activation of autologous T lymphocytes in 4 of 9 experiments.


CONCLUSIONS
These elements showed that Langerhans' cells present in mucosa might play an active role in immune responses to allergens.
Noirey
N
N
INSERM Unité 346, Laboratoire de Recherche Peau Humaine et Immunité, Hôpital Edouard Herriot, Lyon, France.
Rougier
N
N
André
C
C
Schmitt
D
D
Vincent
C
C
D000485:Allergens / Q000276:immunology*; D002469:Cell Separation; D005312:Fetal Blood / Q000166:cytology*; D006801:Humans; D007801:Langerhans Cells / Q000166:cytology*; D008213:Lymphocyte Activation / Q000276:immunology; D010873:Pinocytosis / Q000276:immunology; D011058:Pollen / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D013234:Stem Cells / Q000166:cytology; D013601:T-Lymphocytes / Q000276:immunology*
D000485:Allergens; D011994:Recombinant Proteins