What is the key distinguishing feature of T-cells compared to other lymphocytes?

• A. Large size
• B. Presence of T cell receptor on cell surface
• C. Production of antibodies
• D. Ability to transform into pharmacological agents

Answer: (B)

The key distinguishing feature of T-cells compared to other lymphocytes is the presence of the T cell receptor (TCR) on their cell surface. This receptor is crucial for T-cells to recognize specific antigens presented by other cells, especially those presented in the context of major histocompatibility complex (MHC) molecules. This ability to recognize and respond to particular antigens is what differentiates T-cells from other types of lymphocytes, such as B-cells.

B-cells, for instance, primarily focus on producing antibodies to target pathogens, while T-cells play various roles, including directly killing infected cells (cytotoxic T-cells) or helping other immune cells communicate (helper T-cells). The other options do not capture this fundamental aspect; T-cells are not characterized by their size nor are they involved in the production of antibodies or transforming into pharmacological agents. Instead, their unique TCR enables them to play a critical role in the adaptive immune response.