CD8Korezeptoren

CD8Korezeptoren are co-receptors expressed on CD8+ T lymphocytes that facilitate the recognition of antigenic peptides presented by MHC class I molecules. They are typically assembled as CD8αβ heterodimers on most peripheral CD8+ T cells, while a CD8αα homodimer form is found on certain thymocytes and intraepithelial lymphocytes. As co-receptors, they work in concert with the T-cell receptor (TCR) to enhance sensitivity to peptide–MHC I complexes.

Structurally, CD8Korezeptoren have an extracellular domain that binds to the α3 domain of MHC class I. Their cytoplasmic tails associate with the protein tyrosine kinase Lck, bringing it into the vicinity of the TCR–CD3 signaling complex. This recruitment of Lck accelerates phosphorylation events that initiate downstream T-cell activation following antigen recognition.

Functionally, CD8Korezeptoren increase the avidity and stability of the TCR–peptide–MHC I interaction, lowering the activation threshold for CD8+ T cells. They aid in efficient cytotoxic responses against infected or malignant cells, while the specificity is determined primarily by the TCR. The co-receptor also contributes to thymic positive selection of CD8 lineage during T-cell development.

Expression patterns reflect lineage: CD8αβ is predominant on circulating cytotoxic T cells, whereas CD8αα is enriched on certain gut and epithelial T-cell subsets and some thymocytes. In research and clinical contexts, CD8Korezeptoren are considered in studies of T-cell activation, vaccine design, and adoptive T-cell therapies, where modulating co-receptor engagement can influence responses.