And their quantification method production of IgM by the transformed cells

H chain, L chain, placing a gene encoding the J chain on the same vector, by transforming a suitable host cell, IgM can be obtained pentamer. Gene encoding the J chain may be introduced by co-transformation. Further, in the case without the expression of J chain, IgM is produced as a hexamer. Production of IgM of transformants obtained in accordance with the present invention is high. The present invention provides a method capable of separating quantifying multimeric IgM.