T regulatory cells and HIV infection

Several issues of HIV pathogenesis remain unsolved. Among them, the reason for uncontrolled viral replication in the majority of infected patients is one of the most investigated but still not completely understood. In the last four years a new player has been incorporated into the HIV field: T regulatory (Treg) cells. They are a subset of CD4+ T-cells whose main function is to maintain peripheral tolerance in order to avoid autoimmunity. However, their role in chronic viral and parasitic infections has also been recognized. Several papers have been published in the last years on the potential role of these cells on HIV disease pathogenesis. From the data available so far, two main, nonexclusive roles have been attributed to Treg cells in HIV: a detrimental effect mediated through the impairment of HIV-specific responses, and a beneficial effect by limiting immune activation. The topic is currently highly controversial for different reasons, one of the most important being the lack of standardized assays to measure levels and function of Treg cells.