At the end of the second round of the US Senior Open, a cut is made to reduce the field for the final two rounds. The US Senior Open cut rule is determined is a little bit different than the four other majors and from week-to-week on the PGA Tour Champions.
The US Senior Open cut line is that the top 60 players and ties make the cut. There is no 10-Shot Rule, which would also include any player within 10 shots of the lead.
Week-to-week, the PGA Tour Champions does not have a cut in their 54-hole events, and their two owned-and-operated 72-hole majors (The Tradition and the Senior Players Championship) do not have cuts.
The US Senior Open cut rule doesn't account for a difference between professionals and amateurs. They're treated the same by the US Golf Association.