¹Laboratory of Molecular Immunology, Institute for Molecular and Cell Biology (IBMC) and Molecular Immunology and Pathology, Abel Salazar Institute for the Biomedical Sciences (ICBAS), Porto, Portugal

Correspondence: Dr FA Arosa, Laboratory of Molecular Immunology, Institute for Molecular and Cell Biology, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal, Email: farosa@ibmc.up.pt

Received 19 February 2001; Accepted 3 September 2001.

Abstract

Human peripheral blood CD8⁺ T cells comprise cells that are in different states of differentiation and under the control of complex homeostatic processes. In a number of situations ranging from chronic inflammatory conditions and infectious diseases to ageing, immunodeficiency, iron overload and heavy alcohol intake, major phenotypic changes, usually associated with an increase in CD8⁺ T cells lacking CD28 expression, take place. CD8⁺CD28^– T cells are characterized by a low proliferative capacity to conventional stimulation in vitro and by morphological and functional features of activated/memory T cells. Although the nature of the signals that give origin to this T-cell subset is uncertain, growing evidence argues for the existence of an interplay between epithelial cells, molecules with the MHC-class I fold and CD8⁺ T cells. The possibility that the generation of CD8⁺CD28^– T cells is the combination of TCR/CD3- and regulatory factor-mediated signals as a result of the sensing of modifications of the internal environment is discussed.