Proteolytic cleavage of MHC class I by complement C1-esterases--an overlooked mechanism?
The complement C1-esterases have been shown to cleave the MHC class I molecules, which are important participants in the activation of T lymphocytes, between the alpha 2- and the alpha 3-domain of the heavy chain. The possible involvement of the C1-esterases in the regulation of peripheral self-tolerance is discussed. It is hypothesized that the C1-esterase-mediated cleavage of the MHC class I molecules either induces: a soluble fragment of the outer two domains of the MHC class I molecule, in association with beta 2-microglobulin, to bind to the T cell receptors and prevent the cells from being activated, or produces a change in the exposure of the alpha 3-domain that remain on the cell surface, acting as mediator of a 'veto signal' that prevents these cells from being activated.
Eriksson
H
H
Department of Tumor Immunology, Wallenberg Laboratory, Lund University, Sweden.
D003173:Complement C1s / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
D015395:Histocompatibility Antigens Class I; D003173:Complement C1s