When stimulating PBMC with recombinant human cytokines, how should they be aliquoted and stored to prevent degradation?

<p>Carrier proteins are very important. After conventional research-grade recombinant factors are dissolved, if there is no carrier protein, they are prone to adsorb to the tube wall at low concentrations and degrade. I generally dilute them with buffer containing 0.1% BSA or 10% FBS, but if the PBMC experiment is sensitive to serum batches, it is best to use an animal-component-free diluent or recombinant albumin. When purchasing, you can choose an animal-free grade with endotoxin as low as possible, for example</p>

At the procurement level, it is advisable not to focus solely on the brand; obtain the COA to confirm ED50, endotoxin, purity, and the recommended reconstitution buffer. Research-grade cytokines from major manufacturers such as PeproTech, BioLegend, and R&D typically have clear activity data, and post-opening storage conditions are also clearly stated. When aliquoting, record the lot number and aliquot date, and use the same aliquot batch for experiments within the same batch. If concerned about activity, perform a short-term stability test: measure ED50 at week 1 and week 4 after aliquoting, and compare with your experimental dose. For preclinical studies where downstream procedures may involve reinfusion, then consider animal-component-free or GMP-grade products; for routine stimulation, research-grade is sufficient.

First, change the storage condition to -80°C; -20°C is often insufficient for low-concentration recombinant factors, especially IL-12 and IFN-γ, which tend to lose activity. When reconstituting, use the solvent recommended in the COA, generally PBS/Tris buffer containing 0.1% BSA or 5% trehalose; do not dilute to a low concentration in pure water and then freeze directly. Aliquot into single-use amounts, for example 10-20 μL/tube, using low-binding tubes to avoid repeated freeze-thaw cycles. Take only what you need and do not refreeze the remainder. After aliquoting, it is generally recommended to use within 1-3 months at -80°C; do not store for more than half a year. Before opening each lot, it is best to perform a dose-response assay using a known cell line or PBMC to confirm that activity has not declined.

Recombinant factors must be supplemented with carrier protein before aliquoting; naked liquid stored at -80°C will also lose activity rapidly.

The aliquot volume depends on the experimental usage; 10–20 µL per tube is recommended, and discarding each tube after a single use is the safest approach.