Expression of rat interleukin-5 and generation of neutralizing antiserum: a comparative study of rat IL-5 produced in Escherichia coli and insect cells

Cloning of the rat IL-5Ralpha gene: analysis of 5'-upstream region and expression by B cells

Although rats are widely used for the analysis of allergic reactions and parasitic infections where IL-5 is involved, nothing is currently known of the expression of IL-5 receptor in this species. In this study, the cDNA sequence, genomic structure and the transcriptional regulation of the rat IL-5Ralpha were analyzed. The rat IL-5Ralpha gene, which we localized to chromosome 4q34-q41, spans more than 25 kb and consists of 12 exons. Promoter activity was seen in different cell lines and analysis by deletion experiments allowed to identify two negative regulatory regions which did not differ when tested either with IL-5Ralpha-negative or positive cells. Finally, the investigation of the expression of IL-5Ralpha showed that it is expressed in lung, spleen, liver, and purified rat B cells from normal rat. This can provide an explanation for the role of rat IL-5 as B-cell growth factor and a relevant model in order to better understand the activity of IL-5 on human B cells.

Preparation of recombinant rat interleukin-5 by baculovirus expression system and analysis of its biological activities

Rat interleukin-5 (IL-5) cDNA was subcloned from peritoneal cells collected 4 h after intraperitoneal injection of Ascaris suum antigen solution into the immunized rats. Cysteine proteinase-deleted (CPd) rat IL-5 recombinant virus was constructed by inserting rat IL-5 cDNA into CPd virus having a deletion in the cysteine proteinase gene of the silkworm Bombyx mori nuclear polyhedrosis virus. On infection with the CPd rat IL-5 recombinant virus, the silkworm B. mori larvae produced rat IL-5 as a dimeric form in hemolymph. Recombinant rat IL-5 was purified more than 95.5% by anion-exchange chromatography and hydrophobic chromatography. The purified recombinant rat IL-5 promoted the proliferation of T88-M cells in a concentration-dependent manner, and its effect was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. When bone marrow cells from normal rats were incubated with recombinant rat IL-5 in medium containing methylcellulose, the colony formation by eosinophilic cells was induced. Furthermore, when rat peritoneal eosinophils were incubated with recombinant rat IL-5, the spontaneous decrease in the eosinophil viability was inhibited in time- and concentration-dependent manners. In addition, the recombinant rat IL-5-induced eosinophil survival was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. These findings suggest that rat IL-5 acts as B-cell growth factor II (BCGF-II), eosinophil differentiation factor (EDF), and eosinophil survival-enhancing factor.