McGee makes the case first that the four and twenty elders are representative of the Church in Heaven. And when the seals seem unopenable to John, one of the Church members (one of the elders) tells him that there is someone who can open the seals, is worthy to open the seals. That's not an Angel speaking to John, it is one of the elders.
Then in Rev 7:13 one of the elders/the Church in Heaven explains the ones in white robes are they who came out of the great tribulation and washed their raiment in the blood to be white as snow, showing us that the Church is in Heaven and some are being saved during the Tribulation that are not of the Church taken out in t he Rapture before the Tribulation begins..
“Then in Rev 7:13 one of the elders/the Church in Heaven explains the ones in white robes are they who came out of the great tribulation and washed their raiment in the blood to be white as snow, showing us that the Church is in Heaven and some are being saved during the Tribulation that are not of the Church taken out in t he Rapture before the Tribulation begins..”
The answer to that may be the 144,000 who are sealed:
Revelation 7
http://biblehub.com/kjv/revelation/7.htm