How to verify the inactivation effect of heat inactivated fetal bovine serum before conducting complement related experiments?

Use only about 20 ml each time. It is not recommended to directly buy 500 ml and repeatedly take aliquots from it, unless multiple cell types consume large amounts. A 100 ml small package is more suitable: after opening, aliquot into 20 ml/tube and freeze; use one tube at a time to reduce contamination and freeze-thaw cycles. If the unit price of 500 ml is indeed much lower, it can be purchased and then uniformly aliquoted in a biosafety cabinet into 20 ml or 50 ml centrifuge tubes, labeled with lot number, inactivation date, and number of freeze-thaw cycles, but attention must be paid to sterility and endotoxin control during the aliquoting process. When selecting a supplier, compare whether small-package stock is available, lot-to-lot variation reports, endotoxin and hemoglobin testing data, and transport temperature records. For hybridoma fusion, try to complete key experiments using the same lot number.

To confirm whether complement activity has been removed, looking only at cell status is not sufficiently direct. It is recommended to perform a simple hemolysis test: take a fresh guinea pig or rabbit red blood cell suspension, incubate it with serially diluted inactivated serum at 37°C for 30-60 minutes, and observe hemolysis; if hemolysis still occurs, it indicates that complement has not been completely inactivated. If conditions permit, CH50 can be sent for testing to obtain a more quantitative result. An uninactivated serum can also be used as a positive control, 56°C for 30 minutes as the test group, and 60°C for 30 minutes as the over-inactivation group for side-by-side comparison. For hybridoma fusion, the more critical step is to validate the batch before fusion: confirm that complement activity after inactivation is below the detection limit, and then use it for culture medium preparation.

Heating at 56°C for 30 minutes can inactivate complement in most fetal bovine serum. It is not recommended to readily extend this to 60°C unless it is confirmed that treatment at 60°C does not affect the hybridoma and fusion system. To improve reliability, use a calibrated thermometer and begin timing once the serum temperature reaches 56°C. During the process, gently swirl every 5 minutes, keep the water bath level above the serum level, and immediately cool in ice water after inactivation. The protein content varies among serum lots, and excessive heating can easily cause irreversible turbidity and protein denaturation. A small sample can first be taken for a hemolysis test. If 56°C for 30 minutes is not sufficient, then consider extending 56°C to 45 minutes or using 60°C for a short time, but this must be compared in parallel with cell growth.