to be leavened

基本動詞のleaveとよく似ていますが、leavenは名詞では「発酵した練り粉」「イースト、酵母」を意味し、動詞は「〜に影響を及ぼす、与える」という意味です。ただこれだけではわかりにくいので、Weblio（ちょっとお手軽ですみません...）に行きますと、"to mingle or permeate with some modifying, alleviating, or vivifying element; especially : lighten "という定義がありました。ここは「ボストン市民の温かさが心にしみた、心が軽くなった」あたりでしょう。（UG）

Confusion for marathoners leavened by kindness

It wasn’t what anyone expected on the steady downhill after Heartbreak Hill: Closing in on the 24-mile mark at Coolidge Corner, runners grinding toward the finish of the Boston Marathon were herded to the sides of the course to allow police cars, sirens screaming, to race by.

A half-mile later, race volunteers made an announcement: The finish line had been moved.
At mile 25, a Boston police officer broke the news to those who hadn’t yet finished. “Race is over, folks,” the officer said. “There is no finish line.”

As chaos unfolded at the Boston Marathon Monday, bewildered runners were redirected without explanation. It was the beginning of an hours-long odyssey for the competitors, many of whom were without their cellphones, or money, or anything but thin singlets and shorts. Dazed out-of-towners struggled to find designated gathering spots or their hotels, asking passersby for directions or a call on a cellphone. Many were unable to retrieve their belongings. Most of all, they were cold and exhausted.

Yet many were met with kindness from locals; offered blankets and jackets, cash and food, and a free place to sleep. “People in this city have been unbelievable,” said Glenn Sheehan, 50, a runner born in Wakefield and now lives in South Carolina. “ ‘Let me give you food, let me give you water’ — it’s been like that all afternoon.”

http://www.bostonglobe.com/metro/2013/04/15/runners-try-make-sense-chaos-boston-marathon/uvs54Ywq1sVhIoLZjvpI1J/story.html