The Great Gatsby, to set him off from

I'd like to know if "to set off from" in the following excerpt from the chapter Three of The Great Gatsby means "to distinguish from" or "to keep apart from", "keep away from":

I wondered if the fact that he was not drinking helped to set him off from his guests, for it seemed to me that he grew more correct as the fraternal hilarity increased. When the “Jazz History of the World” was over girls were putting their heads on men’s shoulders in a puppyish, convivial way, girls were swooning backward playfully into men’s arms, even into groups knowing that some one would arrest their falls—but no one swooned backward on Gatsby and no French bob touched Gatsby’s shoulder and no singing quartets were formed with Gatsby’s head for one link.

Thank you.