Cell cloning as a tool to analyze the immune response

Long-term lines of cloned, immunocompetent, non-transformed lymphocytes have the potential to allow the direct examination of many of the key aspects of lymphocyte activation and regulation. We describe here techniques for the long-term propagation of nontransformed human and mouse B-lymphocytes. These lines have the shared characteristics in that they bear membrane Ig, that their growth depends on the presence of appropriate growth factors, and that, when properly stimulated, they secrete Ig. We found that the human lines are negative for Epstein-Barr nuclear antigen and that they can be cloned by limiting dilution. A long-term line of human B-lymphocytes we prepared by limiting dilution cloning contained only lambda light chain-bearing cells.