Grass pollen immunotherapy inhibits allergen-induced infiltration of CD4+ T lymphocytes and eosinophils in the nasal mucosa and increases the number of cells expressing messenger RNA for interferon-gamma.
BACKGROUND
Grass pollen injection immunotherapy is effective in patients with summer hay fever, although efficacy must be balanced against possible side effects. The mechanism of immunotherapy is unknown but may be related to its ability to inhibit allergen-induced late responses, which are known to be characterized by infiltration of T lymphocytes, eosinophils, and cells with messenger RNA for so-called TH2-type cytokines (IL-4 and IL-5).


OBJECTIVE
This study was designed to observe the effect of grass pollen immunotherapy on late nasal responses and associated cellular infiltration and cytokine mRNA expression.


METHODS
We performed local nasal provocation with grass pollen (and a control challenge) in 28 patients after a 12-month double-blind, placebo-controlled trial of immunotherapy. Nasal biopsy specimens were obtained at 24 hours and processed for immunohistology and in situ hybridization studies.


RESULTS
Grass pollen immunotherapy inhibited allergen-induced immediate (0 to 60 minutes) increases in sneezing (p < 0.02) and nasal blocking (p < 0.01) and late (0 to 24 hours) nasal symptoms (p < 0.05). Immunotherapy also inhibited the associated infiltration of the nasal mucosa by CD4+ T lymphocytes and total (major basic protein-containing) and "activated" (cationic protein-secreting) eosinophils (all p = 0.03). There was a significant (p = 0.04) increase in cells expressing mRNA for interferon-gamma at 24 hours after allergen challenge, which correlated inversely with patients' seasonal symptoms (r = -0.65, p < 0.05) and medication requirements (r = -0.75, p < 0.02) during the pollen season.


CONCLUSIONS
The results suggest that successful grass pollen immunotherapy for summer hay fever may act by inhibiting allergen-induced T lymphocyte and eosinophil recruitment and eosinophil activation in the target organ, possibly through a mechanism involving protective local increases in TH1-type cells.
Durham
S R
SR
Department of Allergy and Clinical Immunology, Royal Brompton Hospital and National Heart & Lung Institute, Imperial College, London.
Ying
S
S
Varney
V A
VA
Jacobson
M R
MR
Sudderick
R M
RM
Mackay
I S
IS
Kay
A B
AB
Hamid
Q A
QA
D000328:Adult; D000485:Allergens / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology*; D002634:Chemotaxis, Leukocyte; D016207:Cytokines / Q000235:genetics; D004311:Double-Blind Method; D004804:Eosinophils / Q000166:cytology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D007167:Immunotherapy; D007371:Interferon-gamma / Q000235:genetics; D008297:Male; D009297:Nasal Mucosa / Q000276:immunology*; D009299:Nasal Provocation Tests; D006109:Poaceae / Q000276:immunology*; D011058:Pollen / Q000276:immunology*; D012333:RNA, Messenger / Q000235:genetics; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology / Q000628:therapy*
D000485:Allergens; D016207:Cytokines; D012333:RNA, Messenger; D007371:Interferon-gamma