The addition of an antimicrobial that can be synthesized by the mammalian immune system at the point of challenge may enhance disease resistance. A possible group of agents are cecropins, broad-spectrum antimicrobial peptides, which have been described and characterized. They are relatively non-toxic to normal cells from multicellular organisms but are toxic to a wide range of bacteria, protozoa and fungi, as well as infected and abnormal cells. Twenty-six lines of transgenic mice were produced by pronuclear injection of DNA consisting of the 5-flanking region from –593 to +110 of the mouse interleukin 2 (IL-2) gene, Shiva 1a (a synthetic cecropin-class lytic peptide), and the SV40 polyadenylation/splice signal. A reverse-transcription PCR assay determined that two lines of transgenic mice were produced whose spleen-derived lymphocytes could be induced to transcribe and mature mRNA for Shiva 1a by exposure to 3.25 mg ml–1 of Con A. Two lines were challenged with an inoculation of 5 × 104 Brucella abortus strain 2308. After four weeks, there were significantly fewer B. abortus organisms in the spleens of transgenic mice than in non-transgenic control mice of the same strain (p < 0.05).="" since="" the="" controlling="" regions="" of="" the="" il-2="" enhancer="" and="" the="" amino="" acid="" sequence="" of="" the="" signal="" peptide="" are="" highly="" conserved="" among="" several="" species,="" it="" is="" likely="" that="" this="" recombinant="" gene="" will="" function="" in="" other="">