Immunoblot analysis of the expression of differential λ light chains by HTD8 cells. The pattern of λ light chain secretion was assayed by immunoblotting. (A) The parental HB4C5 cells are shown to secrete only the 32-kD λ light chain. During the continuous culture of HTD8 cells, culture supernatants taken from 0, 2, 3, and 4 weeks after the initial cloning were assessed using an anti-human λ light chain antibody. (B) The HTD8 cells were further cloned by the limiting dilution method in 96-well culture plates, the culture supernatants from 33 randomly chosen wells were subjected to SDS-polyacrylamide gel electrophoresis (PAGE), transferred to a nitrocellulose membrane, and the λ light chains were detected with an anti-human λ light chain antibody/HRP conjugate. (C) Cloned HTD8 cells were cultured in 96-well plates for 4 more weeks, and six randomly selected wells were assayed for λ chain production.