Endotoxins prevent murine IgE production, T(H)2 immune responses, and development of airway eosinophilia but not airway hyperreactivity.
BACKGROUND
Contact with immunomodulatory factors, such as LPS, in early infancy is associated with decreased allergen sensitization.


OBJECTIVE
We sought to study the effects of systemic or airway exposure with LPS on the development of allergen sensitization, eosinophilic airway inflammation, and increased in vivo airway reactivity (AR) in a mouse model.


METHODS
BALB/c mice were systemically sensitized with ovalbumin (OVA) plus adjuvant on days 1 and 14 and challenged through the airways with allergen on days 34 to 36. We performed measurement of OVA-specific IgE serum levels, in vitro T(H)2 cytokine production, differential cell counts in bronchoalveolar lavage fluids, and assessment of in vivo AR to inhaled methacholine by means of barometric whole-body plethysmography.


RESULTS
Systemic LPS administration before OVA sensitization reduced OVA-specific IgE serum levels (426 +/- 76 vs 880 +/- 104 U/mL, P <.01), T(H)2 cytokine production by splenic mononuclear cells (IL-4: 0.08 +/- 0.01 vs 0.17 +/- 0.01 ng/mL; IL-5: 1.98 +/- 0.52 vs 4.11 +/- 0.54 ng/mL; P <.01), and extent of airway eosinophilia (total cell counts: 93 vs 376 x 10(3)/mL; eosinophils: 23% vs 51%; P <.01) compared with that in OVA-sensitized mice. Local LPS administration to sensitized mice before airway allergen challenges particularly induced IFN-gamma production by peribronchial lymph node cells in vitro (1718 +/- 315 vs 483 +/- 103 ng/mL, P <.01) associated with reduced airway eosinophilia compared with that seen in OVA-sensitized mice. Development of increased AR was not affected by systemic or local LPS exposure. Inhibitory effects of LPS on allergen sensitization and eosinophilic airway inflammation were inhibited by administration of anti-IL-12 antibodies before LPS exposure.


CONCLUSIONS
These data indicate that local and systemic application of LPS modulates systemic and local T(H)1/T(H)2 immune responses in a distinct but similarly IL-12-dependent mode.
Department of Pediatric Pneumology and Immunology, University Hospital Charité, Berlin, Germany.
Kerstin
K
Gerhold
Katharina
K
Blümchen
Anja
A
Bock
Christine
C
Seib
Philippe
P
Stock
Tilmann
T
Kallinich
Max
M
Löhning
Ulrich
U
Wahn
Eckard
E
Hamelmann
D000485:Allergens / Q000276:immunology; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004802:Eosinophilia / Q000276:immunology*; D005260:Female; D007073:Immunoglobulin E / Q000096:biosynthesis*; D007249:Inflammation / Q000276:immunology*; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin / Q000276:immunology; D018418:Th2 Cells / Q000187:drug effects* / Q000276:immunology
D000485:Allergens; D016207:Cytokines; D008070:Lipopolysaccharides; D007073:Immunoglobulin E; D010047:Ovalbumin