During the development of multiple sclerosis the destruction of the myelin 
sheath surrounding the neurites is accompanied by citrullination of several 
central nervous system (CNS) proteins, including myelin basic protein and glial 
fibrillary acidic protein. In experimental autoimmune encephalomyelitis (EAE), a 
disease induced in animals by immunization with proteins or peptides from the 
CNS, the animals develop symptoms similar to multiple sclerosis (MS). The 
increased levels of citrullinated CNS proteins associated with MS are also 
observed during the development of EAE. To study the role of CNS protein 
citrullination in EAE development, we induced EAE with a peptide derived from 
myelin oligodendrocyte glycoprotein (MOG(35-55)) in mice lacking the 
peptidylarginine deiminase 2 (PAD2) protein, because this enzyme was the most 
likely candidate to be involved in catalyzing CNS protein citrullination in the 
diseased state. Even though the PAD2 knockout mice displayed a dramatic 
reduction in the amount of citrullination present in the CNS, indicating that 
PAD2 is indeed responsible for the majority of detectable citrullination 
observed in EAE, the development of EAE was not impaired by genetic deletion of 
PAD2, suggesting that PAD2 catalyzed citrullination is not essential to the 
development of EAE.