When our Blessed Mother appeared to St. Bernadette Soubiros in Lourdes, France 150 years ago she identified herself as "The Immaculate Conception". Bernadette had no idea what the name meant and she did not know that earlier, on December 8, 1854, Pope Pius IX had declared that the Blessed Virgin Mary, "in the first instance of her conception by a singular privilege and grace granted by God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved exempt from all stain of original sin." (read the full account at http://www.newadvent.org/cathen/07674d.htm)
Over the years, even though this dogma of our Catholic Faith has been celebrated and proclaimed, many do not understand its meaning, thinking it has to do with Mary's conception of Jesus in her virginal womb. Not so. What we celebrate today is the truth that our Blessed Mother was conceived in the womb of her mother, St. Ann, without the stain of original sin. http://www.advent2008.org/story.php?id=30912
Mary's Immaculate Conception does not consist solely in the absence of original sin, but much more in being "full of grace". The Angel Gabriel's greeting, 'Hail, full of grace, the Lord is with you!' is the strongest testimony of the Immaculate Conception of Mary who would not be full of grace if she had the least stain of sin. She is the mother of the Redeemer and the first of the redeemed, being preserved from the least shadow of guilt by virtue of the merits of her son, Jesus Christ.
What does that mean for us today? The Immaculate Conception is a cause of great joy because with Mary begins our history of salvation. Quoting from the book, "Divine Intimacy" let us consider that "just as in Mary the fullness of grace blossomed into fullness of love for God and humanity, so in every one of us grace should ripen into love toward God and our brothers and sisters - all for the glory of God!"
Let us ask our Blessed Mother to help us grow in grace and in love - in the kind of love that enabled her to say to the Lord, "let it be done to me according to your word."