Use of an automatic cell harvester in a cellular radioimmunoassay

An automatic cell harvester was used in the final step of a cellular radioimmunoassay to collect cell bound anti-rat IgG 125I-F(ab')2. Studies on the reliability of this collection method were performed with antibodies directed against cell surface antigens induced by the Gross murine leukemia virus and produced by immunization of W/Fu rats with the syngeneic (C58NT)D lymphoma. Glutaraldehyde-fixed as well as untreated Gross virus induced lymphoma cells could be used. Similar and specific antibody binding curves were obtained when the cells were incubated with the anti-(C58NT)D serum and anti-rat IgG 125I-F(ab')2 in the presence of 0.1% NaN3. Background levels of non-specific binding of anti-rat 125I-F(ab')2 to mouse lymphoma cells or rat thymocytes were only a few cpm above the background of the gamma-counter. This allowed detection of surface immunoglobulin positive lymphocytes among as few as 30,000 rat splenocytes. In addition, this cellular radioimmunoassay was found to be suitable for the measurement of solubilized cell surface antigen by its capacity to inhibit the binding of the specific antibodies to the target cells.