Human decidua-associated protein hDP200 appears to be a rheumatoid factor

The amino acid sequences of the amino-terminal of the two different polypeptide chains of the human decidua-associated protein hDP200, with apparent molecular masses of 55 and 25 kDa, were determined. The amino-terminal sequence of the 55 kDa chain revealed that it is an immunoglobulin heavy chain, of the VH-III subgroup and the amino-terminal sequence of the 25 kDa chain showed that it is a human kappa V-III light chain. The sequence data indicate that hDP200 is an immunoglobulin. The ability of the hDP200 molecules to form high molecular weight complexes with immunoglobulins of other classes suggest that hDP200 is a rheumatoid factor.