Dear Friends,
The tradition in the East that our Lord Himself used leavened bread during the Mystical Supper is so strong that it is said that when the RC crusaders sacked Constantinople, they broke into a reliquary there that was said to have contained fragments of the bread actually used during the Mystical Supper . . .
It is said that the RC clergy accompanying the crusaders were shocked to see that it was leavened and not unleavened . . .
As Fr Meyendorff wrote, after the Consecration during the Divine Liturgy, however, there is no more bread on the altar but the Body and Blood of OLGS Jesus Christ - whether leavened or unleavened.
Unless, of course, one wishes to go along with what Andrew Rubis says here . . .
Alex