IE 10/11 Open Sans font issue

I have applied font-family- Open sans to asp dropdown list. In IE10, when the drop down is expanded the font is changed to Times New Roman automatically. I

On selecting the item it again displays Open sans font for selected item. In expanded drop down the UI doesn't remain consistent like other browsers.(drop down font changes)

It is working fine at Firefox and Chrome( The Open Sans font remain same).

I have tried adding @font-face{..} and providing Google fonts link, but nothing worked out.

Need help to resolve the issue!

Thanks, in advance.