 Atara Biotherapeutics NASDAQ:ATRA was upgraded by BidaskClub from a buy rating to a strong-buy rating in a research report issued on Friday, BidAskClub reports. Several other research analysts have also recently weighed in on ATRA. Citigroup upgraded shares of Atara Biotherapeutics from a neutral rating to a buy rating and set a 14.00 price objective ... 