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How do CD4 and CD8 help T cells bind to their target cells?
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immune system
Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, TH1 and TH2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.
T cells cannot bind to free-floating antigens; instead, they must recognize foreign protein fragments displayed on the surface of body cells by major histocompatibility complex (MHC) molecules. To facilitate this interaction, T cells utilize surface coreceptors that bind to MHC molecules, providing essential stability to the connection between the T cell and its target.1
The specific coreceptors function as follows:
- CD4: Found on helper T cells, the CD4 coreceptor binds specifically to class II MHC molecules.1
- CD8: Found on cytotoxic T cells, the CD8 coreceptor recognizes and binds to class I MHC molecules.12
By binding to these MHC molecules, these accessory receptors add strength to the bond between the T cell and the target cell, which is critical for effective antigen recognition and subsequent T-cell activation.12