Heat inactivation, in general, decreases the growth promoting properties of the serum and causes increased formation of crystalline or flocculent precipitates (salts, proteins, lipids, fibrin, etc.) in the Fetal Bovine Serum (FBS) as well as in other serum products. In fact, for many cell culture applications, heat inactivation may be unnecessary. Warming the serum-containing medium to 37˚C prior to use, as is the practice in many cell culture laboratories, is often sufficient to inactivate heat-labile complement factors. Heat inactivated FBS is frequently used in immunological applications.Since every cell type has different growth requirements, the choice of whether to heat inactivate your serum or not must be made by the researcher. If you have concerns about whether to use heat inactivated serum with your cell line or not, perform a side-by-side comparison of cell growth with heat inactivated versus non-heat inactivated serum.For your convenience, R&D Systems offers all serum with or without heat-inactivation.