Abstract: Process for the production of proteins with antibody activity in which one or several DNA sequences coding for this protein are introduced into the male pronucleus of a fertilized ovum of a pig or rabbit by microinjection, the ova are implanted in the oviduct of a pig or rabbit, the offspring are bred and the protein with antibody activity is isolated from their serum in the usual way whereby the DNA sequences used for the microinjection are free of bacterial foreign sequences, and are preferably used with immunoglobulin promoter and enhancer sequences.