Successful immunotherapy with the MPL-adjuvanted grass pollen allergy vaccine is associated with the production of allergen-specific IgG antibodies. These blocking antibodies may have protective effects by inhibiting immediate-type reactions and systemic increases of IgE responses caused by seasonal allergen exposure.

Background: The serum tryptase level is used as a diagnostic marker in mastocytosis and is considered to reflect the burden of (neoplastic) mast cells (MC). Methods: In the present study, serum tryptase levels were measured in patients with mastocytosis by fluoroenzyme immunoassay and compared with the extent of infiltration of the bone marrow (BM) by neoplastic MC, determined by tryptase immunohistochemistry. Sixteen patients with cutaneous mastocytosis (CM) and 43 patients with systemic mastocytosis (SM) were examined. Results: In most patients with CM (defined by the absence of dense compact MC infiltrates in tryptase-stained BM sections), normal or near-normal serum tryptase levels (median 10 ng/ml, range 2–23 ng/ml) were measured. By contrast, in the vast majority of patients with SM, elevated serum tryptase levels (median 67 ng/ml) were found. In addition, there was a significant correlation between the grade of infiltration of the BM by neoplastic MC and tryptase levels in patients with SM (r = 0.8). Moreover, enzyme levels differed significantly among the groups of patients with different types of SM. The highest levels (>900 ng/ml) were detected in the patient with MC leukemia, 2 patients with slowly progressing SM and high MC burden (smoldering SM) and 1 patient with indolent SM. In contrast, in all 3 patients with isolated BM mastocytosis (no skin lesions and no signs of multiorgan involvement), serum tryptase levels were <20 ng/ml. Conclusions: In summary, our data suggest that the measurement of serum tryptase is a reliable noninvasive diagnostic approach to estimate the burden of MC in patients with mastocytosis and to distinguish between categories of disease.

An estimated 100 million individuals suffer from birch pollen allergy. Specific immunotherapy, the only curative allergy treatment, can cause life-threatening anaphylactic side effects. Here, we report the genetic engineering of a recombinant trimer consisting of three covalently linked copies of the major birch pollen allergen, Bet v 1. The trimer exhibited profoundly reduced allergenic activity but contained similar secondary structures such as Bet v 1 wild type, Bet v 1-specific B cell and T-cell epitopes, and induced Th1 cytokine release. As immunogen, rBet v 1 trimer induced IgG antibodies, which blocked patients' IgE binding to Bet v 1 and related allergens. Thus, rBet v 1 trimer represents a novel hypoallergenic vaccine prototype for treatment of one of the most frequent allergy forms.

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