Ig light chain variability in DNP494-KLH immunised sea bass (Dicentrarchus labrax L.): Evidence for intramolecular-induced suppression.

The coding sequence of the sea bass light chain was obtained by sequential anchored PCR on a head kidney cDNA library of a DNP494-KLH immunised sea bass. The cDNA sequence obtained codes for a leader peptide of 21 aa and a mature IgL chain of 223 aa. Both the amino acid sequence comparisons and neighbour-joining trees showed that the IgL chain of sea bass obtained is of the L1/G type. To study the variability of the light chain, additional PCRs on the cDNA library and cDNA from pooled head kidneys were performed. Multiple alignment of unique sequences (N = 17) could be performed without introducing gaps, and showed extremely low variability in CDR1, and no variability in CDR2 or CDR3. A possible explanation for this tow variability of the IgL1 chain might be the enhanced expression of monospecific anti-DNP antibodies. The isolation and characterisation of partial genomic and cDNA IgL sequences, which showed normal variability, corroborate this explanation. (C) 2001 Elsevier Science Ltd. All rights reserved.