NF-κB is a transcription factor that plays a pivotal role in a number of physiological cell processes such as growth, apoptosis, and immune response through regulating the expression of a number of cellular genes. The NF-κB family includes five members: cRel, RelB, p65(RelA), p50(p105, precursor of p50), and p52(p100, precursor of p52), which form homo- or heterodimers when in active status. Normally, NF-κB is inactive and retained in the cytoplasm bound to its inhibitory protein IκB. Upon stimulation of various factors such as infection of pathogens including viruses and bacteria or treatment of cytokines such as IL-1 or TNF-α, IκB proteins are phosphorylated, ubiquitinated and finally degraded. Released NF-κB proteins then form homo- or heterodimers, most commonly p50/p65 or p50/p50, which are transported into the nucleus where they bind to specific DNA sequences of targeted genes and activate transcription. NF-κB also induces expression of its own inhibitor, IκBa, which binds to active NF-κB in the nucleus to terminate the induction of gene expression.

Upon receipt, the positive control should be removed and stored at -20^° or -80^°C. The remainder of the kit can be stored for up to 6 months at 2-8^°C from the date of shipment. Opened Microplate Wells or reagents may be stored for up to 1 month at 2^° to 8^°C. Return unused wells to the pouch containing desiccant pack, reseal along entire edge. Note: The kit can be used within one year if the whole kit is stored at -20^°C upon receipt. Avoid repeated freeze-thaw cycles.