High frequency of loss of human kappa light chain expression in mouse-human heterohybridomas.

The expression of human immunoglobulin (Ig) chains in human-mouse heterohybridomas was investigated on the days after cell fusion. Heterohybridomas were made by fusion of mediastinal lymphocytes from lung carcinoma patients and murine (BALB/c) myeloma P3U1. Most (more than 76%) of heterohybridomas easily lost the light chain rather than the heavy chain expression in the early stages after cell fusion. Frequency of loss of kappa-chain expression was predominant, whereas the expression of heavy chain and lambda-chain was rather stable in comparison with that of kappa-chain. These were also confirmed at the clonal level, demonstrating that only lambda-chain but not kappa-chain producers were successfully enriched. In fact some heterohybridomas producing human Ig of lambda-chain type established were found to be quite stable for more than 2 years without any recloning procedures.