Biological Systems MCAT Practice Exam

Where do T cells undergo maturation?

1. Bone marrow

2. Thymus gland

3. Lymph nodes

4. Spleen

The correct answer is: Thymus gland

T cells undergo maturation in the thymus gland. This process is crucial for developing functional and self-tolerant T cells, which are essential for the adaptive immune response. In the thymus, precursor cells derived from bone marrow migrate and mature into T lymphocytes. This maturation involves both positive and negative selection processes. Positive selection ensures that T cells can recognize self-major histocompatibility complex (MHC) molecules, which is vital for their future role in immune responses. Those that successfully recognize self-MHC are allowed to survive, while others that cannot are eliminated. Negative selection removes T cells that strongly recognize self-antigens, preventing autoimmunity. Immature T cells leave the bone marrow and enter the thymus, where they will undergo these critical maturation processes before becoming fully functional T cells, ready to enter the peripheral circulation and perform their immune functions. The other locations mentioned, such as the bone marrow, lymph nodes, and spleen, play roles in different aspects of the immune system, but they're not the primary sites for T cell maturation.