In Revelation 14:4 John tells us that the 144,000 are not defiled by women, but are virgins. This doesn’t sound very politically correct in today’s context, but we need to remember we are speaking in a context familiar to the Scriptures. Moreover, if taken literally, the Scriptures seem to celebrate the life of the male celibates, but this isn’t Scripturally sound. The blessing of God is upon those who marry (Genesis 1:22, 28; Proverbs 5:18-19; 18:22). As for not being defiled by a woman, that pertains to not being defiled, because these people didn’t take an interest in a foreign religion or learn about foreign gods. The context of Revelation 14:4 shows the Lord is married to his people, we are not to defile ourselves by participating in the worship of foreign gods.
What is significant about the 144,000 is that they follow the Lamb wherever he goes. The implication is that they don’t run ahead of him, presuming upon his intentions, nor do they lag behind, not having an interest in where he leads. Nor, are they interested in what may lie to the right or to the left, because they are focused. What interests them is what interests the Lord, and they follow him and only him.
These were redeemed from among men, in that the 144,000 were sinners like everyone else, dead in sin and walking according to the course of this world (Ephesians 2:1-2). The fact is, those of us who are of the 144,000 were by nature no different from the children of wrath, the rebellious who walk according to the way of the dragon of Revelation 12 (cf. Ephesians 2:3). Nevertheless, the Lord quickened our hearts, and raised us from the deathbed of our sinful ways and caused us to rest in heavenly places, in order that we may walk in his steps (cf. Ephesians 2:4-6, 10; 1Peter 2:21). Moreover, according to John, the 144,000 had no deceit, subtlety or guile (i.e. trickery – G1388) in their mouths, which is probably a allusion to Revelation 13:5-6, which points to the false prophet. They are not like him, but rather like the Lamb (Revelation 11:5cf. 19:15, 21).
These are called the firstfruits to God and the Lamb (Revelation 14:4; cf. James 1:18). The idea of firstfruits is that it was offered to honor the Lord (Exodus 34:26-27; Proverbs 3:9). It was that first part of the whole harvest that was used to thank God for the abundance that would be reaped (Numbers 3:13). It was this part of the harvest that blessed the whole harvest of the land (Proverbs 3:9-10).
In Romans 11:16 Paul uses a lump of dough to express this idea. He says: “If the first piece of dough is holy, the lump is also…” (NASB). The first piece is holy, because it is dedicated to God. Therefore, if what is dedicated to God is holy, then that which it came out of must also be holy, because you cannot take that which is corrupt from what is corrupt and offer it to God and expect him to be pleased (cf. Malachi 1:6-8). If this logical use of the Scriptures is accurate, then either the 144,000 represented the firstfruits in the first century AD who would represent all believers who would follow, i.e. all believers being the rest of the harvest, meaning the 144,000 represents all believers of every age. 
If the latter is true, then we need to consider the idea of universal salvation, because the firstfruits would be that first part of the harvest that represents the whole. So, either the 144,000 are the first century believers ONLY, or the 144,000 are the believers of every age (the number being a complete and perfect number) making them the firstfruits of the greater harvest of mankind, meaning everyone God has created from Adam to the present—all are saved, as seems to be concluded by Paul: “Who gave himself a ransom for all, to be testified in due time” (1Timothy 2:6), and “…we trust in the living God, who is the Savior of all men, specially of those that believe.” (1Timothy 4:10).
 See Strong’s Hebrew and Greek Dictionary.