Making specific text bold in a string in C# asp.net

I want make some specific string in bold and bigger in size. Given below is the string.

string body = "TICKET \n";body += "Category : " + Category + "\n";
body += "Priority : " + priority + "\n";body += "Type : " + type + "\n";

From the above string, I want to make specific part bold and larger in size. I want TICKET should be bold and bigger. Help me to find a proper solution. Thank you.