TCR Vβ8+ T Cells Prevent Development of Toxoplasmic Encephalitis in BALB/c Mice Genetically Resistant to the Disease

Abstract

BALB/c are genetically resistant to development of toxoplasmic encephalitis (TE) when infected with Toxoplasma gondii, whereas CBA/Ca mice are susceptible. We compared TCR Vβ chain usage in lymphocytes infiltrated into brains between these animals following infection. TCR Vβ8+ cells were the most frequent T cell population in brains of infected, resistant BALB/c mice, whereas TCR Vβ6+ T cells were more prevalent than Vβ8+ T cells in brains of infected, susceptible CBA/Ca mice. Adoptive transfer of Vβ8+ immune T cells, obtained from infected BALB/c mice, prevented development of TE and mortality in infected athymic nude mice that lack T cells. In contrast, adoptive transfer of Vβ6+ immune T cells did not prevent development of TE or mortality in the nude mice. The protective activity of Vβ8+ immune T cells was greater than that of the total Vβ8− population. In addition, Vβ8+ immune T cells produced markedly greater amounts of IFN-γ than did the Vβ8− population after stimulation with tachyzoite lysate Ags in vitro. Thus, Vβ8+ T cells appear to play a crucial role in the genetic resistance of BALB/c mice against development of TE.