Using a framwork that generates html out of something else (XML but let's not get into the whys and whatfors) and I literally cannot use <em>, <i> or any other

Using a framwork that generates html out of something else (XML but let's not get into the whys and whatfors) and I literally cannot use <em>, <i> or any other tag. I need to use a class and set the style in the CSS file. Edge case? Maybe. Just don't dismiss something that doesn't immediately fit your own use-case.