2 KAPPA-IMMUNOGLOBULIN LIGHT-CHAINS ARE SECRETED BY AN ANTI-DNA HYBRIDOMA - IMPLICATIONS FOR ISOTYPIC EXCLUSION

An anti-DNA hybridoma derived from an MRL/lpr mouse secretes two diffe rent kappa light chains in combination with a single heavy chain. Mult iple single cell clones express and secrete immunoglobulin containing both kappa tight chains. The N-terminal protein sequences of the light chains correspond to sequences predicted from functionally rearranged mRNAs subjected to reverse transcription and amplified by polymerase chain reaction (PCR). Karyotype analysis of the hybridoma indicates a clonal line derived from the fusion of two cells. By amino acid sequen ce comparison and PCR analysis, both functional kappa light chains are derived from the MRL/lpr spleen. The two functional light chain cDNAs were cloned and co-transfected into COS-7 cells with the heavy chain cDNA. Only one of the light chains in combination with mAb 3E10 heavy chain confers anti-DNA reactivity. The presence of two separate kappa light chains and, therefore, two separate antigen receptors on a singl e B cell may have ramifications for both polyclonal activation and tol eration of lupus B cells.