the invention provides a new nerve - derived transglutaminase enzyme that converts immune - derived il - 2 to dimeric il - 2 having oligodendrocyte cytotoxic activity . both the nerve - derived transglutaminase and the dimeric mammalian , e . g . human , il - 2 , are for use as active ingredients in pharmaceutical compositions for inducing and facilitating regeneration of injured nerves of the central nervous system in mammals .