Myeloperoxidase release after allergen-specific conjunctival challenge.

BACKGROUND

Allergen-specific conjunctival challenge is a fruitful and complete tool in evaluating pathophysiological phenomena of allergic inflammation. After challenge, a significant neutrophil infiltrate occurred in allergic subjects. The primary (azurophilic) granules of neutrophils contain a variety of enzymes that might potentiate inflammation, such as myeloperoxidase (MPO). It is not known whether allergen-specific conjunctival challenge (ASCC) is able to elicit MPO release. We also investigated the possible role of immunotherapy (IT) in the release of MPO.

METHODS

The groups studied included Dactylis glomerata-sensitive adult atopic patients suffering from seasonal allergic rhinoconjunctivitis, and healthy adult nonatopic volunteer controls. One group of allergic patients received no specific hyposensitization (not-IT allergic group). A second group of allergic patients had been immunotherapy-treated with Dactylis glomerata extract for the preceding three years and continued to receive a maintenance dose within the highest potency of the extract (IT-allergic group). ASCC with Dactylis glomerata was performed outside the pollen season in all subjects. Myeloperoxidase was assayed by MPO-enzyme immunoassay method.

RESULTS

Thirty minutes after challenge, myeloperoxidase levels in the non-immunotherapy allergic patients were significantly higher compared than in the healthy group (p<0.001). The levels of myeloperoxidase released in the immunotherapy allergic group were significantly lower than those in the nonimmunotherapy allergic group (p<0.001) and higher than those in nonallergic subjects (p<0.001).

CONCLUSIONS

These results indicate that after ASCC there is a release of MPO. Our study suggests that immunotherapy actively modifies the release of MPO after ASCC.