FAQs | PBL Assay Science

The PBL Support Team is here to help you with any question you may have regarding our products. Contact us here for technical inquiry or assistance.

Question	Answer
What is the level of endotoxin of your proteins?	< 1 EU/μg
What is the difference between formulation with carrier protein and formulation with carrier-free?	Carrier protein (PBS with 0.1% BSA) was added to provide extra stability to the cytokine proteins. However, in certain applications, such as in vivo injection, conjugation, or surface binding, carrier protein may interfere.
How to convert interferon specific activity to mass?	The formula to use to convert S.A. to pg/ml is as follow: [(1 x 10E+09)/(Lot specific activity in units/mg)] x [Lot-specific concentration in units/ml]
Why is human interferon beta (Catolog No. 11410) shipped in acetic acid?	Acetic acid prevents aggregation of interferon beta proteins in this particular product formulation.
For interferon beta (Catalog No. 11410), what should I use for dilution?	Culture medium supplemented with serum. Interferon beta proteins are unstable at diluted concentrations. Unless formulation work has been done to verify stability, do not dilute carrier-free solution to protein concentration below 100 μg/ml.

Question	Answer
Does PBL offer controls for its antibodies?	PBL does not offer any controls for its antibodies at the current time.
What control should I use?	For monoclonal antibodies, use normal antibody from the same species and the same isotype. For example, if a MAb is a murine IgG2A, use the normal equivalent as the negative control. Some polyclonal antibodies from PBL are unpurified sera. Therefore, investigators should use normal unpurified serum from the appropriate species as their negative control.
How much neutralizing antibody should I use?	User cell lines vary so there is no specific answer to this question. However, the general rule is 70 fold excess in mass should be used for neutralizing interferon. It is recommended to quantify the amount of interferon via technique such as ELISA. It is also recommended to allow time (1-2 hours in general) for the antibody to neutralize the interferon before adding the virus.
How are antibodies determined to be neutralizing?	The viral challenge assay is used to test antibodies for neutralization activity. The assay measures the ability of the antibody to negate the protective effects of the interferon against the protective effects of the interferon against the viral challenge.

Question	Answer
What types of antibodies are used in PBL ELISA kits?	All PBL ELISA kits are constructed with carefully selected proprietary antibodies and optimized reagents.
What are the specifications for optimization of the reagents for each lot of the kits?	To optimize each lot of kits, PBL modifies the concentration of the reagents to achieve a standard curve that will meet our specific range and signal to noise requirements.
Does PBL offer ELISA reagents separately?	Due to lot-specific optimization of our ELISA kit reagents, they are not sold separately.
Can components from different lots be used as substitutes?	No. Reagent concentration is optimized according to lot. Reagents from different lot can not be used as substitutes without affecting the overall performance of the kit.
Can I use serum or plasma in your assay kits?	PBL offers a range of assay kits that are specifically designed for serum/plasma human interferon alpha (41110, 41115), human interferon beta (41415), mouse interferon beta (42410, 42400), cynomolgus interferon alpha (46100), human IFNs and cytokines (51500).