They went out from us

They went out from us.

What does this passage mean in the epistles of John.

1 John 2:18-19 KJV
Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time. [19] They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.

If you see the body of Christ as the real congregation of the saints, not some local church or local congregation. Then they went out from this universal church spiritually because they weren't born again, they were Antichrists.