US STOCKS-Nasdaq snaps four-day losing streak as health stocks rebound

* Gilead leads as biotechs ends 5-day losing streak

* Railcar makers gain on new tough oil-train safety rules

* Social media stocks fall with LinkedIn

* Consumer sentiment, auto sales rise

* Indexes up: Dow 0.7 pct, S&P 0.7 pct, Nasdaq 0.8 pct (Updates to afternoon)

By Tanya Agrawal

May 1 (Reuters) - Wall Street was higher in afternoon trading on Friday, with the Nasdaq poised to close higher for the first time this week, as healthcare and technology stocks rebounded, and as data pointed to a pick up in economic activity.

A majority of the 10 major S&P indexes were higher, with both the health and tech indexes moving up after two days of losses. The Nasdaq biotech index was up 2.6 percent, ending a 5-day losing streak.

Apple (NasdaqGS: AAPL - news) gave the biggest boost to the Nasdaq and the S&P 500 with a 1.2 percent increase to $126.66. Gilead rose 5.4 percent to $105.94 after its quarterly profit nearly doubled.

Investors were also buoyed by an encouraging batch of data for April that suggested the economy was pulling out of a first-quarter soft patch.

Consumer sentiment jumped and vehicle sales were stronger-than-expected in April, while manufacturing expansion in the month held steady at near a two-year low.

"We anticipate a little bit of a pick up in the second and third quarter," said Paul Nolte, portfolio manager at Kingsview Asset Management in Chicago.

"Its not going to be enough to warrant the Fed to raise rates but its certainly not weak enough to push us into recession."

At 13:39 p.m. EDT (1739 GMT) the Dow Jones industrial average was up 128.08 points, or 0.72 percent, at 17,968.6, the S&P 500 was up 15.29 points, or 0.73 percent, at 2,100.8 and the Nasdaq Composite was up 37.52 points, or 0.76 percent, at 4,978.94.

If the gains hold, all three indexes are on track for their best day since April 20. Still, the three are headed to close lower for the week.

Social media stock were lower as LinkedIn's results capped a weak quarter for the sector. LinkedIn slumped 20.8 percent to $199.66, Twitter (Xetra: A1W6XZ - news) fell 3.8 percent to $37.48 and Facebook (NasdaqGS: FB - news) was off 0.7 percent at $78.23.

Railcar makers gained after tougher oil-train safety standards, including rules to phase out older tank cars in three years, were announced.

Greenbrier gained 5.6 percent to $60.97, while Trinity Industries (NYSE: TRN - news) rose 6.3 percent to $28.82. American Railcar was up 5.3 percent at $55.90.

Yum Brands jumped 6 percent to hit a record high of $91.14 after Daniel Loeb's Third Point revealed a stake in the company.

EnerNOC (NasdaqGS: ENOC - news) soared 18.7 percent to $13.12 after the maker of software to regulate power said it partnered with Tesla in its new battery pack venture.

Expedia (NasdaqGS: EXPE - news) gained 7.9 percent to $101.75 after posting strong results.

Advancing issues outnumbered declining ones on the NYSE by 1,707 to 1,272, for a 1.34-to-1 ratio on the upside; on the Nasdaq, 1,436 issues rose and 1,276 fell for a 1.13-to-1 ratio favoring advancers.

The benchmark S&P 500 index was posting 10 new 52-week highs and no new lows; the Nasdaq Composite was recording 26 new highs and 57 new lows. (Editing by Savio D'Souza)