CLONING AND EXPRESSION OF BOVINE INTERLEUKIN-15 - ANALYSIS AND MODULATION OF TRANSCRIPTION BY EXOGENOUS STIMULATION

The bovine interleukin-15 (IL-15) sequence was cloned from abomasal ly mph node mRNA by enzymatic amplification of cDNA using human primers p roximal to and including the translation start and stop sites. The ope n reading frame is 486 base pairs in length, and the proposed protein sequence shows 78.4% and 73.5% similarity with that predicted for the human and mouse sequences, respectively, Expressed and purified recomb inant bovine IL-15 in the absence of the 48-amino acid leader sequence stimulated the proliferation of bovine lymphoblast cells at least 12- fold over background at maximum concentration levels. Competitive reve rse transcriptase-polymerase chain reaction analysis showed constituti ve levels of IL-15 mRNA within a broad range of tissues and cell types . Lipopolysaccharide addition to adherent lymph node populations cause d moderate increases in IL-15 transcription, whereas the addition of p horbol 12-myristate 13-acetate and calcium ionophore failed to induce gene expression for this cytokine. Transcription of IL-15 was also dow nregulated in the presence of low concentrations of human recombinant interleukin-2.