HJ1 T cells protect against LM infection. (A) Adoptively transferred HJ1 T cells are activated on LM infection. hCD1Tg congenic mice (CD45.1⁺) were adoptively transferred with 1-2 × 10⁷ HJ1 T cells (CD45.2⁺). One hour after transfer, recipient mice were either left alone or intravenously infected with LM. Three days after infection, mice were killed. Single cell suspensions were isolated from the liver of LM-infected or uninfected hCD1Tg congenic mice, stained with mAb against TCRβ, CD69 and CD45.2, and analyzed by flow cytometry. Histograms depict CD69 expression on donor HJ1 T cells based on TCRβ⁺CD45.2⁺ gating (gray: isotype control; dotted line: donor HJ1 T cells from uninfected recipient mice; solid line: donor HJ1 T cells from infected recipient mice). Results are representative of 3 independent experiments. (B-C) Adoptive transfer of HJ1 T cells reduces bacterial burden in hCD1Tg (B) and hCD1Tg/IFNγ^−/− mice (C). hCD1Tg and hCD1Tg/IFN-γ^−/− recipient mice were adoptively transferred with 1-2 × 10⁷ HJ1 T cells. One hour after cell transfer, recipient mice were infected with LM. Three days after infection, spleen and liver were harvested and the bacterial burden was determined. Bar graphs depict the mean ± SD for the bacterial burden in the spleen and liver. Statistical significance was evaluated through comparison of infected mice that had received a transfer of HJ1 T cells and infected recipients that did not receive a transfer. *P < .05; **P < .01. Data were pooled from 4 independent experiments (n = 4 for each group).