PBL Assay Science FAQs

If your questions are not listed below, please contact technical support: technical@stratech.co.uk

Q. What types of antibodies are used in the ELISA kits?

A. All PBL ELISA kits are constructed with carefully selected proprietary antibodies and optimized reagents.

Q. What are the specifications for optimization for each lot of the kits?

A. To optimize each lot of kits, PBL modifies the concentration of the to achieve a standard curve that will meet PBL specific range and signal to noise requirements. In addition we have criteria for: Intra Assay: %CV of replicate wells, %RE of back calculated concentration; and Inter Assay: %CV of back calculated concentration..

Q. Can components from different lots be used as substitutes?

A. No. Reagents concentrations are optimized according to lot. However, components from different kit lots may be used if the component lot is the same. (note: this is especially true for TMB and Stop solutions since the same lot may be used for multiple kit lots).

Q. Can I use serum in yPBL ELISA kits?

A. With the exception of Human Interferon Alpha Serum ELISA kits (product # 41110-1 and 41110-2) and Mouse Interferon Beta ELISA kit (product # 42400-1 and 42400-2), all other PBL ELISA kits are not characterized for use with serum samples.

Q. How much neutralizing antibody should I use?

A. User cell lines may vary so there is no specific answer to this question. However, the general rule is a 70 fold excess in antibody mass should be used for neutralizing interferon. It is recommended to quantify the amount of interferon via techniques such as ELISA. It is also recommended to allow time (1-2 hPBLs in general) for the antibody to neutralize the interferon before adding the virus.

Q. What controls should I use?

A. 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. Many of PBL’s polyclonal antibodies are unpurified sera. Therefore, investigators should use normal unpurified serum from the appropriate species as their negative control.

Q. Does PBL offer controls for its antibodies?

A. PBL does not offer any controls for PBL antibodies at the current time.

Q. How are antibodies determined to be neutralizing?

A. Based on viral challenge assay. The assay measures the ability of the antibody to negate the protective affects of the interferon against the viral challenge.

Q. Level of endotoxin?

A. Endotoxin level is < 0.1 U/µg. PBL limit is 1.0.

Q. The difference between carrier protein and carrier free?

A. Products are sold with a carrier contain protein such as Bovine Serum Abumin (BSA) to ensure stability and prevent aggregates from forming. Products sold without carrier do not contain BSA. Carrier free products recommended in applications including in vivo (in vivo italicized) injection, conjugation, or surface binding assays. (Note: BSA endotoxin level is 0.1-1 U/ml).

Q. How to convert interferon specific activity to mass?

A. The formula to use to convert S.A. to pg/ml is as follows:
(1 x 109 ÷ (Lot specific activity)) x (Lot Concentration (U/ml)= pg/ml.)

Q. Why is human interferon beta shipped in acetic acid?

A. Acetic acid was added to prevent aggregation of interferon beta proteins.


Q. What dilution buffer should I use upon receiving the sample?

A. Refer to product insert for appropriate dilution buffer.



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