Over the past two decades, the revolutionary experiments of Kohler and Milstein have been a major advance in the production of antigen-specific antibodies, In brief, the key to this remarkable advance was the ability to obtain spleen cells from mice that had been immunized with a given antigen and fuse these cells to a non-secreting myeloma cell line, which then produces a single antibody clone when fused with a given B cell present in the spleen cells. Antibody clones are only produced when the mouse B cell fuses with the myeloma line. Non fused B cells are eliminated by a special factor in the medium. The beauty of hybridoma (fused) cell is that it produces only the antibody of a single mouse B cell and is therefore identical throughout its variable and constant regions, and the antibody reacts only with a single determinant on a given antigen. Finally, it is immortal and will produce the same specificity of antibodies for generations. Large-scale culture of these antibodies can provide large quantities of antibody that are precise in their reactivity .