Vector for producing Fc fusion proteins - (Jun/21/2007 )

I have a vector for producing IgG4-Fc fusion proteins, which I want to use for expression of an antigen. The reason for using this vector is that it contains a signal sequence that enables the proteins to be secreted. I am worried about the Fc portion, as I think that its presence might result in the protein binding to Fc receptors. I am thinking of deleting the Fc fragment from the vector, but this poses additional problem as there is a stop codon within it. Does anybody have any experience with IgG4-Fc fusion proteins, and be able to advise me on the relevance of this fragment?

Alternatively, is there somebody out there who can provide me with a plasmid that contains a signal sequence for protein secretion?