Blockers Practical Guide

Recommended Blockers

Blockers for interference in sandwich immunoassays

Animal IgG – Passive Blockers • Suited for mixed species assays (e.g. MAb/PAb) • Species of blocker must be the same as the host of the capture or detection antibody

Active HAMA & RF Blockers • Suited for double mouse monoclonal assays • Removes HAMA, HA & RF interference

Interfering HA (e.g. HAMA) Active HAMA Blocker

Active HAMA Blocker

Mouse IgG BN1300 Recombinant Mouse-FREE IgG A66186M (9-13 mg/ml) A66186M-NA (9-13 mg/ml, Azide Free) A66185M (50-55 mg/ml) A66185M-NA (50-55mg/ml) A66189M (45-55 mg/ml, Proclin) A66190M-NA (30-40mg/ml, Azide Free) N14010M Mouse Serum


Detection Antibody (mouse origin) Capture Antibody (mouse origin) Antigen

Blocking Buffer

HAMA & RF Blockers

CAT No. BN1200

K-Block TM Animal-free HAMA Blocker

TRU-Block TM Ultra



TRU-Block TM TRU-Block TM 3

Rabbit IgG A66100H Sheep IgG A66400S (70-77mg/mL, Liquid)

Goat IgG A66200H Rat IgG A64391R A41182R

A66803H *TRU-Block TM Formulations differ in their ratio of various proprietary ingredients that confers unique blocking characteristics.

In double mouse monoclonal assays, a specific blocker is required to remove a particular type of HA interference called human anti-mouse antibodies (HAMA) and Rheumatoid Factor (RF). A HAMA blocker contains a specific binder directed against all types of heterophilic interference including HAMA and RF. Once bound to the interfering antibodies, an active blocker prevents further binding of HA to other assay components through steric hindrance. Active blockers can typically be used in lower concentrations than passive blocking reagents, which minimizes the reduction in assay signal commonly associated with passive blockers. RECOMMENDED CONCENTRATION: For best performance, the blocker should be included as part of the sample or conjugate diluent, at the recommended concentration range below. In lateral flow assays, the HAMA blocker may be added to the conjugate pad, to a sample diluent or pretreatment buffer, or applied to the membrane as a blocking stripe located before the test stripe:

Passive blocking reagents work by preventing interfering antibodies from binding to the capture or detection antibodies by providing alternate binding sites. Animal IgG (e.g. Goat IgG) can only block one type of interference (e.g. human anti-goat antibodies) so typically more than one type must be used, depending on the host of both the capture and detection antibodies. Animal IgG must be added in excess concentration and the effectiveness depends on the affinity of interfering antibody for the animal IgG. RECOMMENDED CONCENTRATION: • 10x the concentration of the MAb/PAb being used in the assay (e.g. if 5μg/mL of Ab/conjugate, add 50μg/ mL Animal IgG). • Can be added to the sample or conjugate diluent but ideally should be in contact with the patient sample before incubation with the assay capture antibody.

Diluted Samples Undiluted Samples

0.5 ug/mL – 20 ug/mL 5 ug/mL- 200 ug/mL


Blockers Practical Guide

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