A targeting vector was designed to place an internal ribosome entry site (IRES)-enhanced green fluorescent protein (eGFP) fusion protein, downstream of exon 5 of the interleukin 10 (Il10) gene. Homozygous mice are viable, fertile, normal in size, and do not display any gross physical or behavioral abnormalities. Il10 is expressed in leukocytes and other cells and is integral to immune homeostasis. These Vert-X mice exhibit baseline intracellular GFP expression in 1.3% of leukocytes. Specifically, GFP expression was seen in B cells, T cells, myeloid cells, dendritic cells, and Natural Killer (NK) cells. B cells were the predominant expressers of GFP with plasma cells, plasmablasts, and CD19+B220+ cells being the highest expressing. GFP expression was seen in an increased amount of leukocytes after challenge with LPS. These mice may be useful as a tool for studying the localization and initiation of Il10 gene regulation.
