NF-kappaB is a transcription factor of eukaryote, whose family comprises five members in mammals and three in drosophila. Transcription factors of the NF-kappaB family are activated in response to signals that lead to cell growth, differentiation, apoptosis and other events. NF-kappaB takes part in expression of numerous cytokines and adhesion molecules which are critical elements involved in the regulation of immune responses. In this review, we focus on our current understanding of NF-kappaB signal pathway and its role in the innate and adaptive immune responses in which these transcription factors have a key regulatory function. Furthermore we review what is currently known about their effects associated with apoptosis.