Cell therapies using cytotoxic T lymphocytes (CTL’s) are being developed to treat patients with various types of cancers and viral infections. Because of the potential therapeutic applications there is interest in developing culture systems for the expansion of CTL’s in vitro.

A recent report titled “Development of a serum-free medium for in vitro expansion of human cytotoxic T lymphocytes using a statistical design” by Jeon et al. details the composition of such a medium [1]. One of the problems with serum-containing medium is variability caused by undefined serum. Jeon et al. developed a simple serum-free expansion medium that was not only more consistent than serum-containing medium, but also offered more performance. The medium consists of a common base medium (RPMI 1640) supplemented with albumin, an iron source, and other nutrient ingredients. Human peripheral blood mononuclear cells (PBMC’s) expanded in the medium not only grew to higher densities than serum containing medium, but they also retained effector function as determined by cytotoxicity and ELISpot assays.

However, as published, the medium is not animal-free nor is the medium xeno-free. The albumin that was used in the formulation is bovine serum albumin (BSA). BSA has lot-to-lot variability and is a potential source of infectious agents. In addition, BSA is not xeno-free for human therapeutic applications. However, the substitution of recombinant human albumin and insulin in combination with non-animal derived chemical components should enable both animal-free and xeno-free capabilities of the formulation. The substitution of recombinant human transferrin for the iron carrier would also improve the formulation by reducing cell damage due to the oxidative effect of iron compounds.