Major histocompatibility complex class I restricted T-cell autoreactivity in human peripheral blood mononuclear cells

• Published in: Cellular Immunology Vol. 240; no. 1; pp. 62 - 67
• Main Authors: Eleftheriadis, Theodoros, Voyatzi, Soultana, Antoniadi, Georgia, Kartsios, Charalambos, Liakopoulos, Vassilios, Paraskevopoulos, Panagiotis, Galaktidou, Grammatiki
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.03.2006
• Subjects: Antigen processing; Autoimmunity - immunology; Cell Proliferation - drug effects; Cell Separation; Cells, Cultured; Cysteine Endopeptidases - metabolism; Histocompatibility Antigens Class I - immunology; Humans; Interferon-gamma - pharmacology; Interferon-γ; Interleukin-2 - secretion; Lysosomes - drug effects; Phosphorylation - drug effects; Proteasome; Proteasome Inhibitors; Self-tolerance; Subcellular Fractions; T-Lymphocytes - cytology; T-Lymphocytes - immunology; ζ-chain; Self-tolerance; Interferon-γ; Antigen processing; ζ-chain; Proteasome
• ISSN: 0008-8749; 1090-2163; 1365-2567
• DOI: 10.1016/j.cellimm.2006.06.006

During selection in the thymus or any subsequent response, T-cells recognize peptides bound to major histocompatibility complex (MHC) molecules. Peptides produced by lysosomes or by proteasome/immunoproteasome stimulate CD4+ or CD8+ T-cell, respectively. Inflammation alters components of both antigen-processing pathways resulting in the production of different peptides. The role of such changes in self/non-self discrimination was examined in autologous mixed peripheral blood mononuclear cell cultures. Stimulator cells were incubated in the presence or absence of INF-γ, with or without lysosome inhibitors (ammonium chloride/chloroquine), cathepsin inhibitor (E-64), or proteasome/immunoproteasome inhibitor (epoxomicin). Responder cells were added and ζ-chain phosphorylated forms were used as read out. INF-γ did not affect ζ-chain phosphorylated forms, which means that the expected INF-γ induced alterations in antigen processing machinery do not influence self/non-self discrimination. Surprisingly, the completely phosphorylated 23-kDa ζ-chain was always present except in the case of epoxomicin, indicating the presence of MHC class I restricted autoreactive CD8+ T-cells but not of MHC class II restricted autoreactive CD4+ T-cells, possibly due to more efficient negative selection in the thymus of the latter. Autoimmunity is prevented due to absence of help by CD4+ T-cells. This conclusion was confirmed by the lack of differences in IL-2 levels in cell culture supernatants, as well as, by the absence of differences in cell proliferation under the various conditions described above.