Stimulation of interleukin-3 dependent cell growth by specific antibody

We are attempting to raise antibodies against interleukin-3 receptors by immunizing mice with one cloned line of IL-3 dependent cells. In syngeneic mice immunized with a basophil cell line AC-2, serum contains stimulatory activity preferential for the immunizing cells but largely inactive against an alternative IL-3 dependent line of different phenotype. The serum activity corresponds to a fraction containing a cell agglutinin. Supernatants from hybridomas constructed from immune spleen cells raised by direct spleen immunization also contain binding antibodies, of which a select number show phenotype-restricted proliferative activity. We suggest that such antibodies may be recognizing receptors for IL-3, and that phenotypically different IL-3 dependent cells may express different membrane epitopes concerned with interacting with IL-3.