Dicer is an enzyme of the RNase III endoribonuclease family, which is crucial 
for RNA interference (RNAi) in eukaryotes. Dicer is a component of the protein 
machinery (the RNA Induced Silencing Complex [RISC]) which is involved in 
catalyzing the formation of mature microRNAs from their precursors in the 
process of microRNA biogenesis. RISC-associated microRNAs bind to specific 
sequences in the 3' untranslated region of cognate mRNAs largely through 
complementary base pairing, resulting in either translational inhibition and/or 
the degradation of a specific mRNA pool. MicroRNAs epigenetically regulate the 
cellular levels of receptors, transcription factors and signaling proteins that 
govern the developmental pathways and functions of multiple cellular processes. 
The pivotal role played by Dicer in microRNA formation has also piqued the 
interest of molecular immunologists who have sought to understand the biological 
relevance of microRNAs in the development and function of the immune system. 
Here, we review the major findings of these studies and provide an overview of 
the role of Dicer and microRNAs in immune cell development and function. 
Additionally, we highlight deficiencies in our knowledge and new research areas 
that may enhance our understanding of the role of Dicer and microRNAs in 
immunity.