Why heat inactivation matters for immunological work

Fetal bovine serum naturally contains complement proteins — a group of heat-sensitive serum proteins that can lyse certain cell types, interfere with antibody-antigen interactions, and produce non-specific background activity in immunological and virological assays.

Heat inactivation denatures these complement proteins through a controlled 56°C treatment, eliminating complement-mediated interference while preserving the growth-supporting nutrients, hormones and growth factors that make FBS effective for cell culture. This makes heat-inactivated FBS the standard choice wherever complement activity would otherwise confound results.

It is worth noting that heat inactivation provides no additional benefit for routine cell culture that does not involve complement- sensitive assays — for general expansion work, standard or low-endotoxin FBS is typically sufficient and more cost-effective.