Which type of T cells express CD4?

Helper T cells are a specific subset of T cells that play a critical role in the immune response. They are identified by the expression of the CD4 glycoprotein on their surface. This differentiation is key because CD4+ T cells assist other immune cells, such as B cells and cytotoxic T cells, by releasing cytokines that enhance the immune response.

In contrast, while naïve T cells are precursor cells that can develop into different types of T cells upon activation, they do not specifically express CD4 until they mature into helper T cells. Cytotoxic T cells, which are responsible for directly killing infected or malignant cells, express CD8 instead of CD4. Regulatory T cells, which help maintain immune tolerance and prevent excessive immune responses, can also express CD4 but are more specifically characterized by the presence of the transcription factor FoxP3 rather than their CD4 expression alone.

The distinction of helper T cells as CD4+ is essential in understanding their function in orchestrating the immune response, making this option the correct choice.