A method for producing a recombinant dimeric protein, comprising: a) transfecting host cells with a vector enabling expression of a nucleotide sequence coding for a fusion polypeptide, said fusion polypeptide comprising at least the fragment constituted by amino acids in positions 193 to 252 of the β chain of the human C4BP protein or a functional variant of said fragment, said functional variant conserving the capacity to form an at least dimeric protein and being selected from the group constituted by: a1) a modified sequence of the 193 - 252 fragment of the P chain, wherein less than 25% of the amino acids of the 193-252 fragment, preferably less than 10%, have been cut out or replaced, in which the cysteines located in positions 202 and 216 as well as at least 3 amino acids upstream and downstream of each cysteine have been conserved; a2) a modified sequence of the 193 - 252 fragment of the P chain, in which a cysteine responsible for dimerization is substituted with an amino acid selected from alanine, valine, phenylalanine, proline, methionine, isoleucine, leucine and tryptophan, and another amino acid of the fragment is substituted with a cysteine; a3) a sequence of the 193 - 252 fragment of the P chain modified by insertion of a sequence which is heterologous to the P chain, between the cysteines responsible for dimerization; and a4) a sequence of the 193 - 252 fragment of the P chain modified by cutting out amino acids between the cysteines responsible for dimerization; said fusion polypeptide further comprising a polypeptide which is heterologous to said P chain, b) culturing transfected cells under conditions which are suitable for expressing the nucleotide sequence coding for the fusion polypeptide and covalently associating two fusion polypeptides in vivo to form a dimeric protein; and c) recovering the dimeric proteins formed. a) transfecting host cells with a vector enabling expression of a nucleotide sequence coding for a fusion polypeptide, said fusion polypeptide comprising at least the fragment constituted by amino acids in positions 193 to 252 of the β chain of the human C4BP protein or a functional variant of said fragment, said functional variant conserving the capacity to form an at least dimeric protein and being selected from the group constituted by: a1) a modified sequence of the 193 - 252 fragment of the P chain, wherein less than 25% of the amino acids of the 193-252 fragment, preferably less than 10%, have been cut out or replaced, in which the cysteines located in positions 202 and 216 as well as at least 3 amino acids upstream and downstream of each cysteine have been conserved; a2) a modified sequence of the 193 - 252 fragment of the P chain, in which a cysteine responsible for dimerization is substituted with an amino acid selected from alanine, valine, phenylalanine, proline, methionine, isoleucine, leucine and tryptophan, and another amino acid of the fragment is substituted with a cysteine; a3) a sequence of the 193 - 252 fragment of the P chain modified by insertion of a sequence which is heterologous to the P chain, between the cysteines responsible for dimerization; and a4) a sequence of the 193 - 252 fragment of the P chain modified by cutting out amino acids between the cysteines responsible for dimerization; said fusion polypeptide further comprising a polypeptide which is heterologous to said P chain, a1) a modified sequence of the 193 - 252 fragment of the P chain, wherein less than 25% of the amino acids of the 193-252 fragment, preferably less than 10%, have been cut out or replaced, in which the cysteines located in positions 202 and 216 as well as at least 3 amino acids upstream and downstream of each cysteine have been conserved; a2) a modified sequence of the 193 - 252 fragment of the P chain, in which a cysteine responsible for dimerization is substituted with an amino acid selected from alanine, valine, phenylalanine, proline, methionine, isoleucine, leucine and tryptophan, and another amino acid of the fragment is substituted with a cysteine; a3) a sequence of the 193 - 252 fragment of the P chain modified by insertion of a sequence which is heterologous to the P chain, between the cysteines responsible for dimerization; and a4) a sequence of the 193 - 252 fragment of the P chain modified by cutting out amino acids between the cysteines responsible for dimerization; b) culturing transfected cells under conditions which are suitable for expressing the nucleotide sequence coding for the fusion polypeptide and covalently associating two fusion polypeptides in vivo to form a dimeric protein; and c) recovering the dimeric proteins formed.