Enhanced expression of fas ligand (CD95L) on T cells after segmental allergen provocation in asthma.
BACKGROUND
Little is known about the termination of the T-cell driven inflammation found in patients with allergic asthma.


OBJECTIVE
Because signals delivered through Fas/Fas ligand can lead to T-cell apoptosis, we investigated the expression of Fas and Fas ligand on peripheral blood- and bronchoalveolar lavage fluid (BALF)-derived T cells and the percentage of apoptotic BALF cells in asthma.


METHODS
Nine atopic subjects with mild asthma and 9 control subjects underwent segmental sham and allergen challenge. Flow cytometry was used to determine the T-cell expression of Fas and Fas ligand, and the terminal dUTP nick end labeled technique was applied to detect apoptotic BALF cells.


RESULTS
In asthmatic and control subjects almost all T cells in the BALF expressed Fas antigen without changes after saline or allergen challenge. A small percentage of T cells in BALF expressed the Fas ligand. In asthmatic subjects, but not in control subjects, there was a significant increase in Fas ligand after allergen challenge (CD3: 0.8% +/- 0.6% [baseline] vs 3.2% +/- 1.2% [allergen challenge]; CD4: 1.8% +/- 0.0% vs 4.3% +/- 1.8%; CD8: 2.8% +/- 2.4% vs 9.1% +/- 4.8%) but not after saline challenge, with a significant correlation to the percentage of BALF eosinophils. Apoptotic BALF cells were localized exclusively in macrophages at a very low frequency (0.03% to 0.15%) and without changes after saline or allergen challenge in both groups.


CONCLUSIONS
In asthma there is an upregulation of Fas ligand on T cells in BALF after allergen challenge. Because there is no evidence for increased apoptosis, this phenomenon may reflect antigen-induced T-cell activation rather than apoptosis.
Krug
N
N
Department of Respiratory Medicine, Hannover Medical School, Hannover, Germany.
Tschernig
T
T
Balke
K
K
Erpenbeck
V J
VJ
Meyer
L
L
Bode
U
U
Hohlfeld
J M
JM
Pabst
R
R
Fabel
H
H
D000328:Adult; D000485:Allergens / Q000276:immunology*; D017209:Apoptosis; D001249:Asthma / Q000276:immunology*; D001985:Bronchial Provocation Tests; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002452:Cell Count; D053222:Fas Ligand Protein; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis*; D013601:T-Lymphocytes / Q000276:immunology*; D019014:fas Receptor / Q000032:analysis*
D000485:Allergens; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008024:Ligands; D008562:Membrane Glycoproteins; D019014:fas Receptor