Structure and function of major histocompatibility complex class i antigens

Purpose of Review: Major histocompatibility complex (MHC) class I molecules control the repertoire and function of CD8⁺ T cells and NK cells, and both cell types are involved in transplant rejection. Understanding the regulatory role of MHC class I molecules is important in the design of better therapies. This review article focuses on molecular aspects of alloreactive recognition of MHC class I molecules by CD8⁺ T cells and NK cells and on the functional activities of CD8⁺ T cells and NK cells in transplant rejection and tolerance. Recent Findings: Recent T cell receptor (TCR)-peptide-MHC class I crystal structures and structural and functional analyses of MHC class I interactions with NK cell inhibitory receptors have revealed new insights into molecular aspects of allorecognition of MHC class I molecules by CD8⁺ T cells and NK cells. In functional studies, CD8⁺ T cells and NK cells have been shown to have conditional and model-dependent roles in allograft rejection. NK cells have also been shown to have an unexpected role in tolerance induction in the transplantation setting. Summary: Both CD8⁺ and NK cells play diverse roles in graft rejection and tolerance induction. Further understanding of molecular interactions between MHC class I molecules and TCRs or NK receptors is important and highly relevant to transplantation.