Mouse/Human Chimeric Antibodies Directed to Two Nonoverlapping Epitopes of the House Dust Mite Allergen, Der p 2

Chimeric antibody IgE Basophils Histamine release Correspondence to: Dr. Rob C. Aalberse, Department of Allergy Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Plesmanlaan 125, NL–1066 CX Amsterdam (The Netherlands), Tel. (+31) 20 512 3209, Fax (+31) 20 512 3170 The interaction of free allergen with two (or more) IgE molecules bound to the high-affinity receptor for IgE (FcεRI) on mast cells and basophilic granulocytes leads to the release of inflammatory mediators. To study cross-linking of IgE bound to IgE receptors on basophils, we have developed mouse/human chimeric antibodies directed to two non-overlapping epitopes of the house dust mite allergen, Der p 2. These chimeric antibodies were constructed from the heavy-chain variable region and light chain of mu-rine origin, and of the heavy-chain constant region of human origin. We produced chimeric IgE, IgGl and IgG4 antibodies originating from two hybridoma cell lines: 2B12 [1] and αDpX [2]. The chimeric antibodies derived from 2B12, named Dp2A have been described previously [3, 4]. hlgGl and hIgG4-Dp2A antibodies were prepared as well [manuscript in preparation]. For studying cross-linking of IgE bound to IgE receptors present on mast cells, basophils and antigen-presenting cells we also generated a panel of chimeric antibodies directed to another nonoverlapping epi-tope of Der p 2, αDpX. The chimeric αDpX-derived monoclonal antibodies named hIgE-Dp2B, hIgGl-Dp2B and hIgG4Dp2B showed binding to mite extract coupled to CNBr-activated Sepharose (data not shown). The expression level of these chimeric antibodies was about 20, 2,000 and 400 ng/ml, respectively. This shows that the hlgE-Dp2B cell line is by far the lowest antibody-producing cell line. Several attempts to obbain a more productive cell line failed. The nucleotide and deduced amino acid sequences of the V„ domains of 2B12 (Dp2A) and αDpX (Dp2B) are shown in figure 1. This panel of chimeric IgE antibodies enables studying allergen-induced cross-linking. The chimeric IgE antibodies were able to bind to FcεRI present on basophilic granulocytes. Crosslinking of basophil-bound sensitized chimeric IgE by anti-light chain or anti-IgE antibodies resulted in the release of histamine. Only sensitization with a mixture of chimeric Dp2A-IgE and