Hi, according to what I know, mice don't express IL-8 gene, perhaps you should look up for the homologues? 

For a good qPCR assay with proper primer design, our lab follows the MIQE guidelines, maybe you can check out the paper. Hope it helps. 

As far as you know mice do not express this kind of chemokines "IL-8", what you can do is to measure one of the mouse analogues of human IL-8 like Monocyte Chemoattractant protein-1 ( MCP-1 ). Hope this help.......