The Immaculate Conception of the Blessed Virgin Mary was accepted and proclaimed since the first century AD. St Justin Martyr and St Irenaeus were two examples of this posted in our blog (20/01/2013). This blog below is the testimony from the second century by Origen and St Hippolytus.
This Virgin Mother of the Only-begotten of God is called Mary, worthy of God, immaculate of the immaculate, one of the one (Homily 1 [A.D. 244]).
St Hippolytus (170 AD-236AD)
He [Jesus] was the ark formed of incorruptible wood. For by this is signified that His tabernacle [Mary] was exempt from defilement and corruption (Orat. In Illud, Dominus pascit me, in Gallandi, Bibl. Patrum, II, 496 ante [A.D. 235]).