Photograph showing a pair of enlarged human tonsils, the masses of sponge-like lymphoid tissue on either side of the back of the mouth. The tonsils play a role in the bodies response to infection. They produce antibodies for the immune system and also serve to trap and destroy any micro-organisms that should enter the throat. Tonsillitis, inflammation of the tonsils, is due to bacterial or viral infection. It causes a sore throat, fever, and difficulty in swallowing.