Which lymphocyte is responsible for differentiating into helper T cells and cytotoxic T cells?

The correct choice is T cells, which play a crucial role in the adaptive immune response. T cells originate from stem cells in the bone marrow, but they mature in the thymus gland. During maturation, they differentiate into various types, including helper T cells (CD4+ T cells) and cytotoxic T cells (CD8+ T cells).

Helper T cells are essential for activating other immune cells, including B cells and cytotoxic T cells, thus playing a central role in orchestrating the immune response. Cytotoxic T cells are directly involved in killing infected cells or tumor cells. The differentiation process is critical as it allows the immune system to mount specific and effective responses against pathogens.

In contrast, B cells are responsible for producing antibodies and do not differentiate into T cells. Plasma cells are the activated form of B cells that produce antibodies, while natural killer cells are part of the innate immune system and do not require prior sensitization to recognize and destroy infected or cancerous cells.