IL-4 production by human basophils found in the lung following segmental allergen challenge.
BACKGROUND
Human blood basophils secrete high levels of IL-4 following activation with specific allergen, yet their role as cytokine-producing cells in allergic lesions has not been described.


OBJECTIVE
Our objective was to investigate whether and under what conditions basophils infiltrating allergic lesions in the lung secrete IL-4 in vitro.


METHODS
Bronchoalveolar lavage (BAL) cells were recovered 20 hours after segmental allergen challenge. Basophils were enriched with Percoll using a protocol commonly used for blood basophils. IL-4 and histamine were measured in culture supernatants following activation with a variety of stimuli. Two-color flow cytometry was performed to detect intracellular IL-4.


RESULTS
IL-4 protein was detected in all basophil culture supernatants following a 4- to 5-hour incubation in medium alone; the levels obtained did not significantly increase with the addition of anti-IgE. BAL basophils failed to release histamine in response to specific allergen but showed nearly 60% histamine release with N-formyl-methionyl-leucyl-phenylalanine, suggesting that they were desensitized to IgE-mediated stimuli as a result of their activation in vivo. Using these same conditions, IL-4 was not detected in BAL cell fractions enriched for lymphocytes and eosinophils. Ionomycin induced IL-4 secretion by BAL basophils, and this response was reduced with the addition of phorbol myristate acetate. In contrast, phorbol myristate acetate promoted the secretion of IL-4 by BAL cells enriched for lymphocytes; both findings are identical to those reported for basophils and lymphocytes purified from blood. Flow cytometry confirmed the secretion of IL-4 by BAL basophils.


CONCLUSIONS
These data suggest that basophils migrating to the lung following allergen challenge represent a major source of IL-4.
Schroeder
J T
JT
Johns Hopkins Asthma & Allergy Center, Department of Medicine, Division of Clinical Immunology, Baltimore, Md 21224, USA.
Lichtenstein
L M
LM
Roche
E M
EM
Xiao
H
H
Liu
M C
MC
D000485:Allergens / Q000494:pharmacology*; D001491:Basophils / Q000187:drug effects / Q000378:metabolism*; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D005434:Flow Cytometry; D006801:Humans; D015847:Interleukin-4 / Q000378:metabolism*; D008168:Lung / Q000166:cytology* / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D000485:Allergens; D015847:Interleukin-4; D013755:Tetradecanoylphorbol Acetate