what is significant about banquos reply ?

When Macbeth blows off Banquo's request to talk yet again Banquo responds by saying that he'll do whatever Macbeth says as long as he has a clear conscience about it. This tells us he is suspicious about his friend.

So I lose none

In seeking to augment it, but still keep

My bosom franchised and allegiance clear,

I shall be counselled.