Helper T cell IL-2 production is limited by negative feedback and STAT-dependent cytokine signals - PubMed (original) (raw)

Helper T cell IL-2 production is limited by negative feedback and STAT-dependent cytokine signals

Alejandro V Villarino et al. J Exp Med. 2007.

Abstract

Although required for many fundamental immune processes, ranging from self-tolerance to pathogen immunity, interleukin (IL)-2 production is transient, and the mechanisms underlying this brevity remain unclear. These studies reveal that helper T cell IL-2 production is limited by a classic negative feedback loop that functions autonomously or in collaboration with other common gamma chain (IL-4 and IL-7) and IL-6/IL-12 family cytokines (IL-12 and IL-27). Consistent with this model for cytokine-dependent regulation, they also demonstrate that the inhibitory effect can be mediated by several signal transducer and activator of transcription (STAT) family transcription factors, namely STAT5, STAT4, and STAT6. Collectively, these findings establish that IL-2 production is limited by a network of autocrine and paracrine signals that are readily available during acute inflammatory responses and, thus, provide a cellular and molecular basis for its transient pattern of expression.

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Figures

Figure 1.

Figure 1.

IL-2 is required for the natural decay in IL-2 production during helper T cell differentiation. (A–D) Polyclonal CD4+ T cells were CFSE labeled, stimulated with anti-CD3/anti-CD28, and cultured with or without anti–IL-2 mAb. (A–C) After 24, 48, or 72 h, cells were stained for surface CD4 and intracellular IL-2 (n = 6; five experiments pooled in B). (D) Cells were collected at 48 h (no PMA/Iono/BFA), and IL-2 mRNA was quantified by real-time PCR. (E) Monoclonal DO11.10+ CD4+ T cells were CFSE labeled and stimulated with antigen, soluble anti-CD28 mAb, and syngeneic APCs (±anti–IL-2 mAb). IL-2 production was measured after 48 or 96 h. (A–D) Only CD4+ (A and C) or CD4+ DO11.10+ (E) events are shown. RT-PCR data are pooled from five separate experiments.

Figure 2.

Figure 2.

Common γ chain cytokines can suppress helper T cell IL-2 production. (A–C) CFSE-labeled CD4+ T cells were cultured with anti- murine IL-2 mAb and supplemented with recombinant human IL-2 (left to right: 1, 10, 50, and 100 U/ml). As in Fig. 1, flow cytometry and RT-PCR were used to quantify IL-2 production at 72 and 48 h, respectively (n = 3; three experiments pooled in B and C). (D–H) IL-2 production was measured after CD4+ T cells were cultured with recombinant IL-4, IL-7, or IL-15 (±anti–IL-2 mAb; 48 h; n = 3; three experiments pooled in D–F). (A–H) Only CD4+ events are shown.

Figure 3.

Figure 3.

STAT5 is required for IL-2 and IL-4 to suppress IL-2 production. (A–D) CD4+ T cells were isolated from either WT mice (STAT5+/+) or those lacking STAT5a/b in T cells (STAT5 −/−). Cells were cultured with or without anti–IL-2 mAb and, where noted, hIL-2, IL-4, or IL-12 was added. Only CD4+ events are shown (n = 3; compiled in Fig. S2).

Figure 4.

Figure 4.

Helper T cell IL-2 production is limited by Th1- and Th2-polarizing factors. (A) CD4+ T cells were stimulated with anti-CD3 and anti-CD28. At 15 min, 2 h, and 24 h after activation, cells were fixed and permeabilized, and phospho-STAT6 was detected by flow cytometry (not shown: 5, 30, and 60 min; n = 2). (B–D) WT or STAT6−/− CD4+ T cells were cultured as described above (±anti–IL-2 mAb) and, where noted, IL-4 was added (n = 2: two experiments pooled in B). (E) CD4+ T cells were cultured with or without anti–IL-4 mAb (±anti–IL-2 mAb), and IL-2 production was monitored. (F) Phospho-STAT4 was measured after cells were stimulated and stained as in A (n = 2). (G–I) WT or STAT4−/− CD4+ T cells were cultured with or without IL-12 (n = 3: three experiments pooled in G). (A–I) Only CD4+ events are shown.

Figure 5.

Figure 5.

IL-2 can suppress IL-2 responses after immunization. (A–E) CFSE-labeled, DO11.10+ CD4+ T cells were transferred into WT mice, which were immunized 2 d later with antigen-pulsed DCs. At days 2 and 3 after immunization, mice were treated with PBS or IL-2, and 2 d later (day 5 after immunization), LNs and spleens were isolated. (A) Lymphocytes and splenocytes were enumerated by microscopy. Percentages of DO11.10+ CD4+ T cells were determined by flow cytometry and used to calculate the absolute number of antigen-specific cells. (B and C) Surface CD25 was measured directly ex vivo. (D and E) Intracellular IL-2 was measured after restimulation with either (D) OVA-pulsed DCs (16 h) or (E) PMA/ionomycin (4 h). Gray numbers are the percentage of undivided IL-2+ cells, whereas the back numbers denote the percentage of proliferating IL-2+ cells (two mice per group; three experiments pooled in A and B). (F and G) WT mice were populated with DO11.10+ CD4+ T cells, immunized, and treated with IL-2 as above. LNs and spleens were processed at 15 d after immunization (three mice per group; two experiments pooled in F and G). (A–H) For cytokine analysis, all groups were treated with BFA for 2 h before intracellular staining. Only CD4+ DO11.10+ events are displayed.

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