The invention relates to methods for the expression of high yields of the form protein-immunoglobulin fusions having high affinity binding to its ligand, by culturing hosts transformed with DNA encoding the desired fusions in a cultutre system at a low temperature thereby minimizing the amount of misfolded or misbridged protein forms. Said host cells may be transformed mammalian, insect, yeast or bacterial cells. The protein-immunoglobulin fusion may comprises a member of the TNF or TNF-receptor family, such as lymphotoxin-beta or lymphotoxin-beta receptor. The invention also relates to pharmaceutical composition comprising said protein-immunoglobulin fusions.