US stocks gain on optimism over Brexit vote

 US stocks scored solid gains Monday, joining a global equity rally as polls suggested Britain will vote to stay in the European Union.

The gains were a reversal from last week, when polls showing an advantage for the "Leave" faction in Thursday's referendum sparked big declines.

"It's about the momentum shift, the reversal of the momentum of the 'Leave' camp in the Brexit debate shifting to the 'Remain' camp," said Art Hogan chief market strategist at Wunderlich Securities.

The Dow Jones Industrial Average advanced 0.7 percent to 17,804.87.

The broad-based S&P 500 rose 0.6 percent to 2,083.25, while the tech-rich Nasdaq Composite Index gained 0.8 percent at 4,837.21.

Chinese e-commerce giant JD.com rose 4.6 percent on news of an alliance with Wal-Mart Stores in which the US company will transfer its online Yihaodian operations in China to JD.com in exchange for a stake in JD.com. Dow member Wal-Mart rose 0.2 percent.

Anthem and Cigna, two of the nation's top health insurers, were in focus after The Wall Street Journal reported US antitrust regulators are privately expressing concern about Anthem's proposed takeover of Cigna, citing people familiar with the matter. Anthem rose 0.3 percent while Cigna fell 1.3 percent.

Most petroleum-linked stocks rose on higher oil prices, including Chevron, up 1.0 percent, ConocoPhillips, up 1.2 percent, and Apache, up 2.7 percent.

Technology shares with larger gains included Adobe Systems, eBay, Expedia, Priceline and Symantec, all of which climbed 2.5 percent or more. Amazon rose 1.1 percent, while Apple dipped 0.2 percent.