MSP1-specific transgenic T cells respond to P chabaudi in vivo after adoptive transfer into BALB/c Vβa mice. CD4⁺ T cells from B5 TCR Tg (5 × 10⁶) were purified and transferred into Vβa mice (which lack endogenous Vβ8) and infected with 1 × 10⁵P chabaudi parasites. Histogram overlays represent CD69 (A) and CD45RB (B) expression on gated CD4⁺ Vα2/Vβ8⁺ splenocytes from uninfected (thin line) and infected (thick line) recipient mice on the indicated days after infection. (C) Expansion and contraction of anti-MSP-1 T cells during infection. The histogram shows the number of anti-MSP-1 B5 CD4⁺ cells in the spleen, determined from the percentage of CD4⁺Vα2⁺Vβ8⁺ cells and the number of total viable splenocytes. (D) B5 Tg cells make IFN-γ during infection. The mean percentage (of 3 mice) of CD4⁺Vβ8⁺Vα2⁺ cells staining positive for IFN-γ on stimulation. SEMs are less than 10% of the means.