Rights managed images of children with tonsillitis, inflammation of the tonsils. Tonsils are oval-shaped masses of spongy lymphoid tissue on either side of the back of the mouth. They play a role in the body's response to infection, producing antibodies for the immune system and trapping and destroying micro-organisms that enter the throat. Tonsillitis is usually caused by an infection by streptococci bacteria. Images shown here also include quinsy (a peritonsillar abscess involving the tissue surrounding the tonsil), a condition that usually occurs after tonsillitis (inflammation of the tonsils). Pictures and photographs include diagnostic images of patients.