GAMMA-DELTA T-CELL ACTIVATION OR ANERGY DURING INFECTIONS - THE ROLE OF NONPEPTIDIC TCR LIGANDS AND HLA CLASS-I MOLECULES

V gamma 9V delta 2-encoded T cell receptors (TCR) expressed by most hu man peripheral blood gamma delta T cells mediate the recognition of no npeptidic phosphoantigens from various pathogens without any known req uirement for HLA molecules. Functionally mature V gamma 9V delta 2 T c ells display a potent natural killer (NK) -like cytotoxic activity, sh are with NK cells the expression of inhibitory receptors for HLA class I molecules, and release a plethora of cytokines, most notably interf eron-gamma and tamer necrosis factor a. Hence, through local activatio n, the early recruitment and stimulation of V gamma 9V delta 2 T cells may promote efficient anti-infectious immunity. However, a chronic ov eractivation of this T cell subset may result in immunopathology. The meeting held in St. Vincent, Val d'Aosta, Italy (symposium on gamma de lta T cells in natural immunity to infections: a rationale for vaccine development organized by the World Foundation for AIDS Research and P revention, the UNESCO, and the Italian National Research Council, Dece mber 2-4, 1996) focused on the importance of gamma delta T cell activa tion and anergy for the pathogenesis of tuberculosis, malaria, and HIV infections.