Abstract
This report describes studies carried out in an attempt to define the antibody specificity of a rabbit antiserum generated to the RPMI 8226 line of human myeloma cells and then isolate and characterize the antigen. The antiserum reacted to a significantly higher titer in a quantitative semi‐micro complement fixation assay with RPMI 8226 cells as compared to the RPMI 4098 line of human lymphocytes or normal human bone‐marrow cells, particularly after absorption with RPMI 4098 cells. A similar difference in reactivity was also noted for cell‐free lysates of the three different types of cells. A variety of different procedures were carried out to attempt to solubilize the antigens of the RPMI 8226 cell. Of the procedures tried, deoxycholate treatment of sonicated or freeze‐thaw extracts, 3 M KCI, autolysis and papain digestion were found to solubilize antigens from RPMI 8226 cells that reacted with anti‐RPMI 8226 cell serum absorbed with RPMI 4098 cells. Further, the solubilized RPMI 8226 cell antigens did not react with an antiserum to RPMI 4098 cells. Components solubilized from RPMI 4098 cells by similar procedures did not react with the absorbed anti‐RPMI 8226 cell serum to a significant titer. The initial studies carried out to characterize the components solubilized from the RPMI 8226 cell revealed that they were recovered in the included volume after gel filtration on Sephadex G‐200 and that this material consisted of three proteins with approximate molecular weights of 66,000, 55,000 and 31,000 daltons as estimated by electrophoresis on SDS‐acrylamide gels. These results indicate that the RPMI 8226 line of human myeloma cells possesses antigens not found on the RPMI 4098 line of human lymphocytes that can be solubilized and that react with an antiserum generated to intact RPMI 8226 cells.