Which statement describes the final outcome after activation and clonal expansion of T cells?

• A. The T cell binds a co-stimulator and becomes activated
• B. The antigen is presented to B cells
• C. The T cell differentiates into plasma cells
• D. The activated T cell clones proliferate and differentiate into effector and memory cells

Answer: (D)

When T cells are activated and then undergo clonal expansion, the key outcome is the rapid growth and specialization of those cells to fight the antigen. Activation triggers T cells to proliferate, producing many identical clones that can all recognize the same threat. These descendants differentiate into two main pools: effector T cells that actively perform immune functions to eliminate the infection, and memory T cells that persist long-term to respond faster if the same threat appears again. This combination of large-scale expansion plus division into effector and memory cells is what the final outcome looks like after activation and clonal expansion.

The other ideas describe parts of the process or different cell types: requiring a co-stimulatory signal is part of activation, not the final outcome; presenting the antigen to B cells is a B cell activation event; and plasma cells are derived from B cells, not T cells.