You can use the kit, but be warned that its likely at least some - if not most - of the rat kits will not recognize mouse cytokines due to antigenic differences. For example, many human kits will cross react with nonhuman primates, although there is considerable variation by antigen, hybridoma clone, and species you are working with. There is a website for finding antibodies that cross-react with nonhuman primates. You can ask the manufacturer, or do a Google search for the mAb clone being used, someone may have looked to see whether a kit is cross-reactive with other species.