INVIVO EXPRESSION OF INTERLEUKIN-5 INDUCES AN EOSINOPHILIA AND EXPANDED LY-1B LINEAGE POPULATIONS

In vitro, murine interieukin 5 (IL-5) acts as a colony-stimulating factor tor eoalnophils and induces B cells to proliferate and secrete antibody. In order to asseas the biological effects of IL-5 in vivo, we transplanted lethally irradiated mlce wlth bone marrow cells Infected with a recombinant retrovirus bearing the IL-5 coding sequence. Within 2 weeks the peripheral blood of recipient mlce exhibited a marked eosinophilla which persisted for at least 12 months, and an excess number of eosinophils was also evident In the bone marrow, spleen, liver, lung, and gut. Although no changes could be detected In the conventional B lymphocyte population, the perttoneum was replete wlth B cells characteristic of the Ly-1 lineage. Despite these expanded cell populations, mice remained healthy for 12 months after transplantation. These results suggest that IL-5 acts primarily on eosinophils and B cells of the Ly-1 lineage, and that persistent overproduction of these cell types is not pathogenic. © 1990 Oxford University Press.