Which of the following is a characteristic of T cells?

• A. Synthesize antibody
• B. Mature in the thymus
• C. Able to bind unprocessed antigen
• D. Primarily protect against extracellular parasites

Answer: (B)

T cells mature in the thymus, where they undergo development and selection to ensure they recognize peptide antigens presented by MHC molecules and are not strongly reactive to self. This maturation in the thymus is a defining feature of T lymphocytes. Unlike B cells, which produce antibodies, T cells do not synthesize antibodies. T cell receptors recognize processed antigens only when presented by antigen-presenting cells on MHC; they cannot bind unprocessed antigens directly. T cells are central to cell-mediated immunity, defending mainly against intracellular pathogens and abnormal host cells rather than extracellular parasites, which are more typically dealt with by antibody-mediated responses.