title: Unusual CD4+CD28-T Cells and Their Pathogenic Role in Chronic Inflammatory Disorders.
abstract: CD28 is a primary co-stimulatory receptor that is essential for successful T cell activation, proliferation, and survival. While ubiquitously expressed on naive T cells, the level of CD28 expression on memory T cells is largely dependent on the T-cell differentiation stage in humans. Expansion of circulating T cells lacking CD28 was originally considered a hallmark of age-associated immunological changes in humans, with a progressive loss of CD28 following replicative senescence with advancing age. However, an increasing body of evidence has revealed that there is a significant age-inappropriate expansion of CD4+CD28-T cells in patients with a variety of chronic inflammatory diseases, suggesting that these cells play a role in their pathogenesis. In fact, expanded CD4+CD28-T cells can produce large amounts of proinflammatory cytokines such as IFN-γ and TNF-α and also have cytotoxic potential, which may cause tissue damage and development of pathogenesis in many inflammatory disorders. Here we review the characteristics of CD4+CD28-T cells as well as the recent advances highlighting the contribution of these cells to several disease conditions.
authors.affiliation: Department of Biomedical Sciences, Seoul National University College of Medicine and BK21Plus Biomedical Science Project, Seoul National University College of Medicine, Seoul 03080, Korea.
authors.forename: Ga Hye
authors.initials: GH
authors.lastname: Lee
authors.affiliation: Department of Biomedical Sciences, Seoul National University College of Medicine and BK21Plus Biomedical Science Project, Seoul National University College of Medicine, Seoul 03080, Korea.; Department of Microbiology and Immunology, Seoul National University College of Medicine; Ischemic/Hypoxic Disease Institute and Institute of Infectious Diseases, Seoul National University College of Medicine; Seoul National University Hospital Biomedical Research Institute, Seoul 03080, Korea.
authors.forename: Won-Woo
authors.initials: WW
authors.lastname: Lee
keywords: CD28; CD4+CD28− T cells; Chronic inflammatory diseases; Co-stimulatory receptor; Cytotoxic potential