Which type of T-cells exclusively recognize MHC II molecules?

Helper T-cells specifically recognize MHC class II molecules. These molecules are primarily expressed on professional antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells. When a helper T-cell encounters an antigen presented on MHC class II, it forms a critical interaction that activates the T-cell. This activation is essential for orchestrating the adaptive immune response, as helper T-cells release various cytokines that stimulate other immune cells, including B cells to produce antibodies and cytotoxic T-cells to kill infected or cancerous cells.

This specialization of helper T-cells for MHC class II is central to their role in the immune system, as it allows them to recognize and respond to extracellular pathogens that are processed and presented by APCs. Understanding this distinction is crucial for comprehending how different T-cell types contribute to immunity and how vaccines and therapies are designed to enhance immune responses.