Did Christianity transform Rome or did Rome change Christianity?

I think it could be said that Christianity and Rome had a significant effect on each other.  Having said that, Christianity benefited more from the relationship, with many historians believing that the religion may have had a hand in the downfall of Rome.  The upstart religion had the effect of changing the culture and tradition of the empire of Rome, which is something that some historians point to as a cause of the fall.  On the other hand, when the Roman Empire adopted Christianity — first making it legal, then christening it as the official religion — Christianity automatically gained millions of converts.  In 380 AD, Christianity gained prominence in Rome and it became illegal to worship other gods.  This allowed the church to develop an economic and political structure that permitted it to become one of the dominant forces in Europe for centuries to come.