Recombinant proteins are a core component in many proteomics experiments. In the simplest experiments researchers use recombinant protein products as concentration standards or positive controls for in vitro assays like ELISA or Western blotting. More complex experiments may make use of recombinant proteins with confirmed biological activity. An active recombinant may be introduced in vivo to stimulate a desired outcome or measure the effect of a particular protein on cellular physiology. For example, recombinant CD-40L/CD-154 can be introduced to PBMCs in culture in order to simulate infection induced macrophage activation and stimulate CD-40 dependent production of IL-8.
The purity and consistency of a recombinant protein plays a major role in any technique, but it is particularly important when utilizing this sort of in vivo methodology. Animal derived growth factors or cytokines may be present in recombinant protein preparations because animal products (like BSA) are frequently used in traditional recombinant protein manufacturing processes. These contaminants may not be detectable through traditional methods for assessing purity, but even at trace concentrations they can alter physiological response and skew results in an unpredictable manner.