Figure 1. PGE₂ signaling directly suppresses CTL function via the receptors EP2 and EP4 during LCMV infection.

(a) Ptger2 and Ptger4 mRNA was measured using qRT-PCR in PD-1^hi and PD-1^intermediate CD44^hi CD8 T cells from LCMV-CL13 infected mice at day 21 p.i. Data are from two independent experiments with a total of 13 mice per group. (b) Whole splenocytes from mice infected with LCMV-Arm or LCMV-CL13 were harvested at day 8 p.i. and cultured for 24 hours. PGE₂ was measured in the supernatant by ELISA. Data are from two independent experiments with a total of 8 mice per group. (c–d) Congenically labeled WT or EP2/4 DKO P14⁺ TCR CD8 T cells were adoptively transferred into WT mice depleted of CD4 T cells and infected with LCMV-CL13. At day 8 p.i., P14⁺ CD8 T cells were stimulated with GP_33-41 peptide with or without 40μM PGE₂ for 5hrs and stained for LAMP-1 and intracellular cytokines (IFN-γ, TNF-α, and IL-2). (c) Representative dot plots on left show LAMP-1 and IFN-γ production by P14⁺ CTLs and those on right show TNF-α and IL-2 production by IFN-γ⁺ P14⁺ CTLs. (d) Scatter plots show the compiled frequency of cytokine producing cells in the absence or presence of PGE₂. Data above were compiled from three independent experiments with 13 total WT and 14 total EP2/4 DKO mice. (e) Congenically labeled WT or EP2/4 DKO P14⁺ TCR CD8 T cells were adoptively transferred into WT mice and infected with LCMV-Arm. At day 8 p.i., P14⁺ CD8 T cells were stimulated with GP_33-41 peptide with or without 40μM PGE₂ for 1hr. Phosphorylated ERK (pERK) and S6 (pS6) were measured by flow cytometry. Data for part e are representative of 3 independent experiments with a total of 9 mice per group. Data analysis was performed by ANOVA for part b, and by unpaired two-tailed t-test for parts a and d. Error bars depict S.E.M. *P < 0.05, **P < 0.01, and ***P < 0.001.