If you have reasonable equipment, 43 is possible. As an I gear, your Frenzy ability allows you to actually damage people many levels higher. I am 48, and I occasionally PvP. As an I gear, I have managed to take down a level ~60 with my quest 40 items in a strait dogfight. If you PvP at this level, expect a lot of deaths, and few kills, but it is possible to actually help out your team at that level (just get used to the idea of dying a lot...)

Recommended level, I don't know though...