Jerusalem Famine Relief: Jerusalem was the home of the Apostles, the center of Christianity, and specifically the center of Jewish Christianity -- Jews who had converted to Christianity.
Antioch was the center of Gentile Christianity -- non-Jews who had become Christians.
There was a major cultural difference between Jewish Christians (Jewish beliefs and culture) and Gentile Christians (primarily Greek culture).
In about the year 47 there was a famine affecting Jerusalem. The fact that Paul and Barabas brought famine relief from Antioch to Jerusalem, shows us that there was unity in Christianity's leadership despite the differences. (See Jerusalem Council).