House dust mites Dermatophagoides pteronyssinus (Dpt) are among the most frequent causes of allergy symptoms in Europe. Der p 1 is one of the major allergenic compounds of Dpt and the pathological Der p 1-specific B cells play a key role as producers of allergen-binding antibodies. The selective elimination of these cells by artificial protein molecules which inhibit the production of Dpt-recognizing IgE antibodies is a perspective therapeutic goal of allergy. A protein engineered chimeric molecule has been constructed, which binds Der p 1-specific B cells via their BCR and suppresses selectively the production of anti-Der p 1 antibodies via CR1. The synthetic peptide Der p 1 p52-71 and an anti-CD35 monoclonal antibody were used for the construction of Der p 1 chimera. The functional effects of engineered antibodies were analyzed in vitro using PBMCs from allergy patients. Significant inhibition of allergen-specific proliferation and reduction of Der p 1-IgE antibody production were observed after treatment of PBMCs from allergic patients with Der p 1-peptide chimera. Culturing of these PBMCs in the presence of the chimeric molecule increased the percentage of apoptotic (Annexin V-positive) B lymphocytes, but not T lymphocytes.