a first experiment which was fundamental , described in 1973 , discusses the immune response to various antigens of an asterid : asterina gibbosa . it indicated ( leclerc , 1973 ) , more exactly , the specific immunocytochemical response to hrp ( horse - radish peroxydase ) of the sea star . the general idea that emerged from the experiments made in our laboratories was that echinodermata ( leclerc and brillouet , 1981 , delmotte et al . , 1986 , leclerc , 2012 ) , as exemplified by sea stars ( asterina gibbosa and asterias rubens ) , possessed an immune system able to mount cellular and humoral - specific responses after stimulation with a foreign antigen . in 2011 sea star antibody was shown to correlate to ig kappa genes ( leclerc et al . , 2011 ) and in 2013 a  true  candidate ig kappa gene was found ( leclerc et al . , 2013 ) . we report the sequence and deduced amino - acid composition of the sea star ig kappa gene . we used the experimental protocol concerning the smart kit pcr cdna synthesis ( clontech ) on the candidate gene cdna sequence ( leclerc et al . , 5cagtcattaaaaggacatgataatttcggaccgggtctttaatattacaatgactgctgctatgcgtggc aacatggcgtctctatggatgttcttctttgtcgtggggataactttacaacggagtttggcgatttaca cgtttcgcgagcaaccgtcggacactagcgcgttgcaggggagcacagtggtgcttcactgctccgttga gcagtacataaacaccacggccatcgtttggtggagccgtgactcggtcatcagccacaacaaagacctg aaactgtccagtctaaacaccgaccagctccaaaggtactcgatttcaggcgacgcatctcggggggaat tcaaccttagaatagtgaactttaccgccacagacgccgccagttaccgctgtcagatgtttgcg3 we purified the polya fraction , according a specific kit and generated the c dna with an oligodt . a non - specific amplification was performed and followed by a specific one with an oligo 956 forward ( 53 ) 5-cagattcagaaacacatgtatttcc-3 and then an oligo 957 reverse ( 53 ) 5-tttagcatggcatgtaaagacacc-3 , always requested for this experiment ( clontech ) . the pcr products showed , in agarose gel , many bands for the negative control , and one band ( 400  bp ) for the specific pcr . the results show that the revealed gene , after sequencing , shows only little gene described in the previous paper ( leclerc et al . , 2013 ) it is enough to decipher this gene to realize it ; here is the sequence as shown in fig .  1 . based on sander 's review ( sander and schneider , 1991 ) , we propose that this gene relates to immunoglobulins as it contains 2 typical cysteines of the domains of ig , without being able to assert , at the moment , if it is about a heavy or light chain of immunoglobulins . a single indication ( delmotte et al . , 1986 ) favors the light chain due to the observed molecular weight ( 30,000  da : delmotte et al . another antigen such as hapten ( leclerc and brillouet , 1981 ) could produce another type of  antibody  currently , we do n't know , at the moment , if there are several types of antibody in the sea star a. rubens . what we are sure , on the other hand ( because there is a gene ( the sea star ig kappa ) ) , the function of which is the one of the defenses of the sea star against the immunopathogenicity attacks ; the hrp , in the present case . in terms of amino - acid , our gene could present 118 amino - acids as shown in fig . this is slightly smaller than the true ig kappa region v - iv s107b which is reported to be 129 amino - acids found in mammals . in conclusion , this antibody gene of sea star calls back the mouse ig kappa region v - iv s107b precursor gene but is different from it by the number of amino - acids ( 118 instead of 129 aa ) . our data contributes to knowledge the molecular and genetic bases of non - self recognition by invertebrates which will allow further comprehension of the evolution of mhc antigens and immunoglobulins .