First Republic Bank maintained its lead as the top contributor to jumbo mortgage-backed securities issued in the first quarter of 2015, according to a ranking by Inside Nonconforming Markets. First Republic was identified as contributing $1.43 billion to jumbo MBS issued during the quarter, accounting for 31.0 percent of all jumbo MBS activity. The bank was also the top jumbo MBS contributor for all of 2014, with $1.46 billion in identified contributions ... [Includes one data chart]