Isolation of cDNA encoding immunoglobulin light chain from common carp (Cyprinus carpio L.)

cDNA clones partially encoding immunoglobulin (lg) light (L) chain variable (V) region associated with constant (C) region were isolated from carp (Cyprinus carpio L.) spleen by reverse transcription-polymerase chain reaction (RT-PCR) using degenerated primers corresponding to the conserved amino acid sequences in N-terminus of VL domain and in middle of CL domain. The VL region is readily delineated into framework regions (FR) and complementarity-determining regions (CDR). cDNA clones encoding complete CL domain were then obtained by a rapid amplification of cDNA 3′-end method (3′-RACE). The sequences of both VL and CL region contain well conserved cysteine residues important for intra- or interdomain interaction in mammals. Comparisons of the amino acid sequence of the CL domain with those of other species showed the highest degree of similarity of 59%, 55%, and 54% to those of rainbow trout IgL 1 isotype (Oncorhynchus mykiss), channel catfish G isotype (Ictalurus punctatus), and Atlantic cod (Gadus morhua L.), respectively. Multiple sequence alignments of the CL domain with those of higher vertebrate, however, did not readily allow it to be classified as κ or λ isotypes. Genomic Southern blot analyses using VL-and CL-specific probes showed that there are at least 13 VL segments and 14 CL segments in the genome of the carp, indicating that IgL locus of carp has a cluster-like organisation similar to those of several teleost species.