MEASUREMENT OF IGE ANTIBODIES AGAINST PURIFIED GRASS-POLLEN ALLERGENS(LOL-P-1, LOL-P-2, LOL-P-3 AND LOL-P-5) DURING IMMUNOTHERAPY

Background IgE titres tend to rise early after the start of immunother apy, followed by a decline to pre-immunotherapy levels or lower. Objec tives We were interested to know whether the early increase in IEE ant ibodies includes new specificities of IgE, and whether these responses persist. Methods Sera of 64 patients undergoing grass pollen immunoth erapy were tested for IgE against four purified grass pollen allergens : Lol p 1, 2, 3, and 5. At least two serum samples were taken, one bef ore the start of therapy and one between 5 and 18 months after the fir st immunization (mean: 10 months). Results The mean IgE responses to L ol p 1, 2 and 3 showed a moderate but not significant increase. In con trast, the mean IgE response to Lol p 5 showed a significant decrease of >30%. IgE against total Lolium perenne pollen extract moderately in creased (>20%), showing that a RAST for total pollen is not always ind icative for the development of IgE against its major allergens. For >4 0% of the patients it was found that IgE against one or more of the fo ur allergens increased, while IgE against the remaining allergen(s) de creased. For 10 sera the ratio of IgE titres against at least two alle rgens changed by at least a factor of 5. The changes in specific IgE a lso included conversions from negative (< 0.1 RU) to positive (0.6 to 5.0 RU) for five patients. For two patients, the induction of these 'n ew' IgE antibodies against major allergens was shown to result in a re sponse that was persistent over several years. Conclusion Although act ive induction of new IgE specificities by immunotherapy was not really proven, the observations in this study indicate that monitoring of Ig E against purified (major) allergens is necessary to evaluate changes in specific IgE in a reliable way.