Upon initial thawing, recombinant human IL-2 (Cat. No. 554603) should be aliquoted into polypropylene microtubes and frozen at -80°C for future use. Alternatively, the product can be diluted in sterile neutral buffer containing not less than 0.5 - 10 mg/mL carrier protein, such as human or bovine serum albumin, aliquoted and stored at -80°C. For in vitro biological assay use, carrier-protein concentrations of ≥ 1 mg/mL are recommended. For use as an ELISA standard, carrier-protein concentrations of 5 - 10 mg/mL are recommended. Failure to add carrier protein or store at indicated temperatures may result in a loss of activity. Recombinant human IL-2 should not be diluted to less than 10 µg/mL for long term storage. Carrier proteins should be pre-screened for possible effects in each investigator's experimental system. Carrier proteins may have an undesired influence on experimental results due to toxicity, high endotoxin levels or possible blocking activity.
ELISA Standard: Recombinant human IL-2 (Cat. No. 554603) is useful as a quantitative standard for measuring human IL-2 protein levels using sandwich ELISA with purified 5344.111 (Cat. No. 555051) as a capture antibody and biotinylated B33-2 (Cat. No. 555040) as the detection antibody. To obtain linear standard curves, investigators may want to consider using doubling dilutions of recombinant human IL-2 from
2,000 - 15 pg/mL to be included in each ELISA plate. For measuring human IL-2 in serum or plasma, investigators are highly encouraged to use the BD OptEIA™ Human IL-2 Set (Cat. No. 555190) and BD OptEIA™ Human IL-2 Kit II (Cat. No. 550611 ).
Bioassay: Investigators are advised that the Bioassay application is not routinely tested for this material and are highly encouraged to both titrate this material and include appropriate controls in relevant experiments. An activity range of 0.06 - 1.0 x 10^9 units/mg, encompassing an
ED50 = 10 - 150 pg/mL, has previously been reported using CTLL-2 as indicator cells for proliferation, with a unit defined as the amount of material needed to stimulate a half-maximal response at cytokine saturation.
Blocking: Recombinant human IL-2 (Cat. No. 554603) can be useful as a blocking control for flow cytometric analysis when used with a fluorochrome-conjugated antibody, such as PE-conjugated MQ1-17H12 (Cat. No. 559334). Investigators are advised that the blocking application is not routinely tested for this material. Intracellular cytokine staining techniques and the use of blocking controls are described in detail by C.Prussin and D.Metcalfe.