Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Organs of the lymphatic system include the tonsils, thymus gland and spleen. The thymus gland produces T cells or T-lymphocytes (see below) and the spleen and tonsils help in fighting infections. The spleen's main function is to filter the blood. The spleen also detects viruses and bacteria and triggers the release of pathogen fighting cells. Answer: t cells
A:
What does the thymus gland produce?