Predominant activation and expansion of Vγ9-bearing γδT cells in vivo as well as in vitro in salmonella infection

γδ T cell receptor-positive cells (γδ T cells) have recently been implicated to play a role in the protection against infectious pathogens. Serial studies on γδ T cells in 14 patients with salmonella infection have revealed that the proportions of 76 T cells (mean±SD: 17.9±13.2%) in salmonella infection were significantly increased (P < 0.01) compared with 35 normal controls (5.0±2.6%) and 13 patients with other bacterial infections (4.0±1.4%). Expansion of 78 T cells was more prominent in the systemic form (28.9±10.8%) than in the gastroenteritis form (10.5±7.9%) of salmonella infection (P < 0.01). Most in vivo-expanded γδ T cells expressed Vγ 9 gene product. Increased activated (HLA-DR+) T cells were observed in all the six patients with the systemic form and four of the seven with gastroenteritis form. Especially in the six with systemic form, γδ T cell activation was significantly higher than αβ T cell activation at the early stage of illness (P < 0.01). When peripheral blood lymphocytes from normal individuals were cultured with live salmonella, γδ T cells were preferentially activated and expanded and most of them expressed Vγ 9. Purified γδ T cells also responded to live salmonella in vitro. The present study suggests that human γδ T cells play a role in the protec-tion against salmonella infection in vivo.