Chemical typing of human kappa light chain subgroups expressed by human hybrid myelomas

Hybrids between human spleen cells and the non-secretor NSO mouse myeloma, and also between the rat non-secretor line YB2/O and human peripheral blood cells were prepared. After a month in culture very few hybrids retained the ability to secrete the human kappa light chain. From these, clones could be derived which remained stable over several months of continuous culture. On incorporating [3H]-Leu into the culture medium the cells secrete large amounts of radioactive light chain. It is shown that, even without dialysis, the purity of the preparation is sufficient for an automatic N-terminal sequence analysis at the radioactive level. From the pattern of distribution of leucine in the first twenty-two amino acid residues, it is possible to assign the synthesized light chains to one of the four established human subgroups. The method permits a fast and simple classification of human light chains secreted by hybrid myelomas. Although tested with rodent x human hybrids, we see no reason why the method could not equally apply to human x human hybrids.