Basophil activation during pollen season in patients monosensitized to grass pollens

Background: Basotest(R) is a new basophil-activation test based upon the ex pression of CD63 (gp53) in the presence of allergens. It is an effective di agnostic test for pollen-allergic patients. However, it is not known whethe r Basotest results differ during the pollen season. Methods: We examined the activation of basophils by Basotest in 13 patients sensitized only to grass pollen, before and during the pollen season, in o rder to assess whether Basotest could be used as a diagnostic test during t he pollen season. Dose-response curves with IO-fold increasing concentratio ns of timothy grass pollen (10(-4) to 100 AU) were carried out. Results: Basophils were not activated spontaneously during the pollen seaso n since the CD63 expression was below detectable levels before in vitro cel l activation. A decreased percentage of activated basophils at the peak of activation was found in comparing the pre- and in-season tests, but all pat ients had a positive test. When basophil activation was at its peak, the al lergen concentration was similar during the two periods. Moreover, the medi an area under the curve was significantly (P < 0.02) reduced during the sea son as compared to before the season. Conclusions: Basotest can therefore be used as a diagnostic test during the pollen season, but the allergen exposure needs to be characterized if quan titative studies are performed.