This Small Business Innovation Research (SBIR) Phase II project proposes to develop a rapid IgSwitch Assay for inducing and isolating IgG class switch variants from IgM hybridomas using in-vitro culture conditions, microencapsulation technology and fluorescence activated cell sorting. The IgSwitch Assay is expected to be a significant improvement over conventional methods used to isolate class switch variants, and will be useful in cell line development and monoclonal antibody production. Prior Phase I research has already demonstrated the feasibility of the proposed method using a model IgM hybridoma. This Phase II project will develop in-vitro culture conditions that promote switching to different IgG subclasses. The Phase II research will also validate reagents for a family of isotype specific IgSwitch Assays. <br/><br/>The commercial application of this project will be in the area of monoclonal antibodies. Use of the targeted IgSwitch Assay in monoclonal antibody production will help to generate new IgG specific antibodies from a largely untapped source of IgM hybridomas, for potential use as research, therapeutic, diagnostic, and imaging reagents.