TRAIL deficiency does not rescue impaired CD8+ T cell memory generated in the absence of CD4+ T cell help - PubMed (original) (raw)

TRAIL deficiency does not rescue impaired CD8+ T cell memory generated in the absence of CD4+ T cell help

Jilian A Sacks et al. J Immunol. 2008.

Abstract

Ag-specific CD8(+) T cells immunized in the absence of CD4(+) T cell help, so-called "unhelped" CD8(+) T cells, are defective in function and survival. We investigated the role of the proapoptotic molecule TRAIL in this defect. We first demonstrate that TRAIL does not contribute to the CD8(+) T cell response to Listeria monocytogenes strain expressing OVA (LmOVA) in the presence of CD4(+) T cells. Secondly, we generated mice doubly deficient in CD4(+) T cells and TRAIL and analyzed their CD8(+) T cell response to LmOVA. Memory CD8(+) T cells in double-deficient mice waned over time and were not protective against rechallenge, similar to their TRAIL-sufficient unhelped counterparts. To avoid the effects of CD4(+) T cell deficiency during memory maintenance, and to address whether TRAIL plays a role in the early programming of the CD8(+) T cell response, we performed experiments using heterologous prime and early boost immunizations. We did not observe activation-induced cell death of unhelped CD8(+) T cells when mice were infected with followed vaccinia virus expressing OVA 9 days later by LmOVA infection. Furthermore, primary immunization of CD4(+) T cell-deficient mice with cell-associated Ag followed by LmOVA infection did not reveal a role for TRAIL-mediated activation-induced cell death. Overall, our results suggest that CD4(+) T cell help for the CD8(+) T cell response is not contingent on the silencing of TRAIL expression and prevention of TRAIL-mediated apoptosis.

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Conflict of interest statement

Disclosures

The authors have no financial conflicts of interest.

Figures

FIGURE 1

FIGURE 1

TRAIL deficiency does not affect the kinetics or magnitude of the primary and secondary CD8+T cell responses to LmOVA. WT and TRAIL−/− (TR−/−) mice were infected with 2000 CFU LmOVA. A, The bacterial burden in the spleen was determined at the indicated time points postinfection. Each point is an individual mouse. The limit of detection was 100 CFU as indicated by the dotted line. B, At the indicated time points after infection, the OVA-specific response in the blood (day 7) and spleen (day 53) was quantified by tetramer staining and ICS following 4 h in vitro peptide stimulation (OVAp). FACS plots are gated on CD8+ T cells with at least two mice per genotype. The frequencies of cytokine producers indicated at the day 53 time point are the percentages of cells in each gate minus the background of the no peptide control (No pep). C, Each point indicates the average percentage of IFN-γ+CD8+ T cells ± SEM in the blood or spleen at the indicated time points postinfection. Data are representative of at least 2–3 mice per time point. D, Fifty-seven days after primary infection, WT and TR−/− mice were infected with 5 × 105 CFU LmOVA. Three days after infection the bacterial burden in the spleen and the OVA-specific response in the spleen and liver were quantified. A control mouse that had not been immunized before was infected with the same high dose (Naive). The FACS plots are gated on CD8+ T cells and are representative of 2–3 mice per genotype.

FIGURE 2

FIGURE 2

Despite TRAIL deficiency, CD8+ memory T cell numbers and function decline in the absence of CD4+ T cells. WT, MHC class II−/− (MHCII−/−), and double knockout TR−/− × MHCII−/− (Dbl KO) mice were infected with 2000 CFU LmOVA. A, Seven days postinfection the level of OVA-specific cells in the blood was determined by tetramer staining and ICS. All FACS plots are gated on CD8+ T cells. Data are representative of at least 3 mice per genotype. B, Expression of IL-7R_α_ by tetramer-positive cells was determined at day 7. Histograms are gated on KbOVA+CD8+ T cells. C, Sixty-seven days postinfection, OVA-specific memory levels were assessed in the spleen. The FACS plots are gated on CD8+ T cells. Blood from an unimmunized WT mouse was used as a tetramer staining control. D, Cytokine expression by the memory cells. The FACS plots are gated on CD8+ T cells, and the lower histograms depict the percentage of IL-2+ cells of IFN-_γ_-producing CD8+ T cells, with the gray lines indicating expression by CD8+ T cells from the same animals that were not restimulated with peptide (No pep). Data are representative of 2–3 mice per genotype.

FIGURE 3

FIGURE 3

TRAIL deficiency does not restore impaired recall response of CD8+ T cells observed in the absence of CD4+ T cell help. Seventy-one days following primary infection with LmOVA WT, MHCII−/− and Dbl KO mice were infected with 2 × 105 CFU LmOVA. The bacterial burden and OVA-specific response were assessed 3 days later. Mice of each genotype that had not been immunized before were infected as controls (Naive). A, The OVA-specific recall response in the spleen was determined by tetramer staining and ICS. All FACS plots are gated on CD8+ T cells. B, The absolute number of KbOVA+CD8+ T cells was quantified in the spleen of mice that were not rechallenged (day 67 post primary infection) and in other mice that were rechallenged (3 days postrecall at 71 days after primary infection). The numbers on the graph indicate the fold expansion. C, Three days after rechallenge, the bacterial burden in the spleen was determined. The dotted line indicates the limit of detection. Data depict the average CFU/spleen of 2–3 mice per group ± SEM.

FIGURE 4

FIGURE 4

Early secondary challenge reveals no role for CD4+ T cell help or TRAIL. Mice of the indicated genotypes were infected with 2 × 106 PFU Vacc-OVA i.p. A, The OVA-specific response was analyzed 7 days later by tetramer staining in the blood. FACS plots are gated on CD8+ T cells and show the average ± SEM of 2– 4 mice per group. An uninfected mouse is shown as a tetramer staining control (No Vacc-OVA). B, Nine days after primary infection, mice were infected with 2 × 104 CFU LmOVA i.v. The OVA-specific response was analyzed 5 days later in the spleen (day 14) by tetramer staining. FACS plots are gated on CD8+ T cells and are representative of 2– 4 mice per genotype. A WT mouse infected only with LmOVA 5 days before is shown (No Vacc-OVA).

FIGURE 5

FIGURE 5

Absence of TRAIL does not rescue cells primed by a helper-dependent immunogen. Mice of the indicated genotypes were immunized with 107 irradiated Act-mOVA splenocytes s.c. and 10 days later were infected (B) or not (A) with 4 × 104 CFU LmOVA i.v. The OVA-specific response was analyzed 4 days later (day 14 after cellular immunization) by ICS in the spleen. FACS plots are gated on CD8+ T cells. Numbers indicate the frequency of cytokine-producing CD8+ T cells in each gate. C, The absolute number of IFN-_γ_-producing cells was quantified in the spleen. Frequencies were determined by subtracting the staining from the no peptide control. Naive WT mice infected with LmOVA 4 days before are shown as a control. Data represent the average of at least two mice per genotype ± SEM.

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