Grass pollen immunotherapy: symptomatic improvement correlates with reductions in eosinophils and IL-5 mRNA expression in the nasal mucosa during the pollen season.
BACKGROUND
Tissue eosinophilia and infiltration by T(H)2-type T cells are characteristic features of allergic rhinitis both after allergen challenge and during natural allergen exposure. Specific immunotherapy inhibits allergen-induced nasal eosinophilia.


OBJECTIVE
We sought to assess, in the context of a randomized trial, the relationships between symptomatic improvement after immunotherapy and eosinophil numbers and IL-5 expression in the nasal mucosa during the pollen season.


METHODS
Nasal biopsy specimens were taken from 37 adults with severe summer hay fever at baseline (out of season) and at peak season after 2 years of treatment with a depot grass pollen extract or placebo. Biopsy specimens were processed for immunohistochemistry by using mAbs against eosinophils (EG2), T cells (CD3), and IL-2 receptor-positive cells (CD25), as well as for in situ hybridization by using a sulfur 35-labeled antisense riboprobe directed against IL-5.


RESULTS
Immunotherapy significantly reduced symptoms (49%, P =.01) and medication requirements (80%, P =.007) compared with placebo. There was a 400% increase (P =.004) in eosinophils during the pollen season in placebo-treated patients, which was inhibited in the immunotherapy group (20% increase, P =.04 between groups). Seasonal increases were also observed for CD25(+) cells (P =.002), CD3(+) cells (P =.02), and IL-5 mRNA-expressing cells (P =.03) in the placebo group but not in the immunotherapy group. A significant correlation was observed between eosinophils and IL-5 expression (r = 0.5, P <.05). Both eosinophils (r = 0.6, P <.02) and IL-5 (r = 0.6, P <.02) correlated with symptoms after immunotherapy.


CONCLUSIONS
Improvement in symptoms after grass pollen immunotherapy may result, at least in part, from inhibition of IL-5-dependent tissue eosinophilia during the pollen season.
Wilson
D R
DR
Department of Upper Respiratory Medicine, Imperial College School of Medicine at The National Heart and Lung Institute, Dovehouse St., London, SW3 6LY, UK.
Nouri-Aria
K T
KT
Walker
S M
SM
Pajno
G B
GB
O'Brien
F
F
Jacobson
M R
MR
Mackay
I S
IS
Durham
S R
SR
D001706:Biopsy; D003888:Desensitization, Immunologic; D004311:Double-Blind Method; D004804:Eosinophils / Q000166:cytology / Q000276:immunology*; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D015848:Interleukin-5 / Q000378:metabolism*; D009297:Nasal Mucosa / Q000378:metabolism; D006109:Poaceae / Q000276:immunology*; D011058:Pollen / Q000276:immunology*; D012333:RNA, Messenger / Q000378:metabolism; D006255:Rhinitis, Allergic, Seasonal / Q000628:therapy*; D013601:T-Lymphocytes / Q000276:immunology
D015848:Interleukin-5; D012333:RNA, Messenger