Background: Allergens in Plantago lanceolata have not been characterized yet. The objective was to characterize some plantain-pollen allergens and to investigate the cross-reactivity between plantain and grass pollens.
Methods: Sera from four patients monosensitive to plantain pollen and from eight grass-pollen-allergic patients showing strong skin reactivity to plantain pollen in the skin prick test (SPT) underwent immunoblot analysis with both Plantago and grass mix extract. Moreover, immunoblot inhibition experiments were done with grass mix extract as inhibitor.
Results: All four sera from plantain-allergic patients reacted to two distinct bands at 17 and 19 kDa, and 2/4 sera showed further reactivity to a 40-kDa protein, which in one case represented the most prominent IgE-binding allergen. Plantain-monosensitive subjects did not show any reactivity to grass-pollen extract, and preabsorption of their sera with grass-pollen extract did not cause any loss of reactivity to plantain pollen. Sera from all eight grass-pollen-allergic controls reacted to a 30-kDa protein in plantain pollen, and some sera showed cross-reactivity to higher and lower molecular-weight structures as well. In all cases, plantain reactivity was totally abolished by preabsorption of sera with grass-pollen extract. A preliminary investigation by immunoblot showed that polyclonal IgG anti-Phl p 5 (but not polyclonal Phl p 1) from rabbit reacted to a 30-kDa protein in plantain pollen.
Conclusions: Three specific allergens (of 17, 19, and 40 kDa, respectively) have been detected in plantain pollen. Further studies on a larger number of patients will determine whether these proteins may be considered major allergens. Cross-reactivity between grass and plantain pollen is mainly caused by a 30-kDa protein in plantain pollen. Group 5 grass-pollen allergen is probably responsible for most grass/plantain cross-reactivity.