▁protein ▁of ▁the ▁transfer rin ▁family . ▁L act o fer rin ▁is ▁a ▁glob ular ▁g ly cop rote in ▁with ▁a ▁mole cular ▁mass ▁of ▁about ▁ 8 0 ▁k Da ▁that ▁is ▁widely ▁represented ▁in ▁various ▁secret ory ▁flu ids , ▁such ▁as ▁milk , ▁sal iva , ▁tears , ▁and ▁nas al ▁secret ions . ▁L act o fer rin ▁is ▁also ▁present ▁in ▁secondary ▁gran ules ▁of ▁PM N s ▁and ▁is ▁secret ed ▁by ▁some ▁ac inar ▁cells . ▁L act o fer rin ▁can ▁be ▁pur ified ▁from ▁milk ▁or ▁produced ▁recom bin antly . ▁Human ▁col ost rum ▁(" first ▁milk ") ▁has ▁the ▁highest ▁concentration , ▁followed ▁by ▁human ▁milk , ▁then ▁cow ▁milk ▁( 1 5 0   m g / L ). ▁ ▁L act o fer rin ▁is ▁one ▁of ▁the ▁components ▁of ▁the ▁imm une ▁system ▁of ▁the ▁body ; ▁it ▁has ▁ant im icro b ial ▁activity ▁( b acter io cide , ▁fung ic ide ) ▁and ▁is ▁part ▁of ▁the ▁inn ate ▁defense , ▁mainly ▁at ▁m uc oses . ▁In ▁particular , ▁la ct o fer rin ▁provides ▁ant ib acter ial ▁activity ▁to ▁human ▁inf ants . ▁L act o fer rin ▁ ▁interact s ▁with ▁DNA ▁and ▁R NA , ▁pol ys ac char ides ▁and ▁he par in , ▁and ▁shows ▁some ▁of ▁its ▁bi ological ▁functions ▁in ▁complex es ▁with ▁these ▁lig ands . ▁ ▁History ▁Occ urrence ▁of ▁iron - cont