NFAT5 and Hypernatremia: Several studies have shown that the minimal level of hypernatremia at which immune cells (macrophages, T lymphocytes) activate NFAT5-dependent responses or exhibit functional defects if they lack this factor would be around 360–380 mOsm/kg, roughly equivalent to adding 30–40 mM extra sodium to a standard RPMI or DMEM culture medium.