The immunoglobulin light chain in poikilothermic vertebrates

The immunoglobulin light chains are classified as kappa or lambda in mammal s and birds (homeothermic vertebrates), but the traditional criteria for th is classification are not applicable to the light chains found in poikiloth ermic vertebrates. Still it is possible to find some relationships between Ig light chain sequences in these animals and in those of the homeothermic animals. It is generally accepted that the Ig light chains contribute to th e antigen binding capacity of antibodies and the variability is approximate ly similar in all studied vertebrate species except the elasmobranchs. This might be explained by the organisation oi the Ig light chain locus in thes e animals and the fact that the variable and joining DNA segments are joine d in the genome. These conclusions are limited by the small number of speci es studied in this respect.