Expression of HLA class I-specific inhibitory receptors by chronically activated cytolytic T lymphocytes: useful or harmful to the host?

T cells, primarily chronically activated cytolytic T lymphocytes (CTL), can express human leukocyte antigen class I-specific inhibitory receptors previously identified in natural killer cells. Engagement of these receptors leads to inhibition of CTL function. Although the receptor expression may represent a safety device to prevent autoimmunity, it may result in the inability to control viral spread or tumour growth, i.e. two main functions of CTLs. The physiopathologic implications of this event are discussed.