The immune system recognizes the presence of pathogens by several proteins that bind to molecules secreted by the pathogen or carried on their surface. The cells responsible for these immune responses include the B-Cells, T-Cells, macrophages, neutrophils, basophils, eosinophils, endothelial cells, or mast cells (Ref.1). These cells have distinct roles in the immune system, and communicate with other immune cells by cytokines, which control proliferation, differentiation and function of cells of the immune system. Furthermore, they are involved in processes of inflammation and in the neuronal, haematopoietic and embryonal development of an organism.

NF-KappaB (Nuclear Factor-KappaB) is a heterodimeric protein composed of different combinations of members of the Rel family of transcription factors. The Rel/ NF-KappaB family of transcription factors are involved mainly in stress-induced, immune, and inflammatory responses.

RNAi, or RNA interference, was discovered when puzzling results were obtained in experiments conducted by biologists Su Guo and Kenneth Kenpheus. They observed that sense and antisense RNA were equally effective in suppressing specific gene expression (Guo and Kempheus, 1995). In 1998, Fire and his colleagues resolved this paradox by finding that small amounts of dsRNA contaminate sense and antisense preparations. Even earlier, biologists had unknowingly observed RNA interference when performing experiments on Petunias.

Transcriptional repression is an essential mechanism in the precise control of gene expression. Transcriptional repressor proteins associate with their target genes either directly through a DNA-binding domain or indirectly by interacting with other DNA-bound proteins. To inhibit transcription in a selective manner, a repressor protein can (1) mask a transcriptional activation domain, (2) block interaction of an activator with other components of the transcription machinery, or (3) displace an activator from the DNA. Furthermore, DNA response elements can exert allosteric effects on transcriptional regulators, such that regulators may activate transcription in the context of one gene, yet repress transcription in another (Ref.1).