Role of CD4+ T-cells for regulating splenic myelopoiesis and monocyte differentiation after experimental myocardial infarction.

Myocardial infarction (MI) induces the generation of proinflammatory Ly6Chigh monocytes in the spleen and the recruitment of these cells to the myocardium. CD4+ Foxp3+ CD25+ T-cells (Tregs) promote the healing process after myocardial infarction by engendering a pro-healing differentiation state in myocardial monocyte-derived macrophages. We aimed to study the effects of CD4+ T-cells on splenic myelopoiesis and monocyte differentiation. We instigated MI in mice and found that MI-induced splenic myelopoiesis is abrogated in CD4+ T-cell deficient animals. Conventional CD4+ T-cells promoted myelopoiesis in vitro by cell-cell-contact and paracrine mechanisms, including interferon-gamma (IFN-γ) signalling. Depletion of regulatory T-cells enhanced myelopoiesis in vivo, as evidenced by increases in progenitor cell numbers and proliferative activity in the spleen 5 days after MI. The frequency of CD4+ T-cells-producing factors that promote myelopoiesis increased within the spleen of Treg-depleted mice. Moreover, depletion of Tregs caused a proinflammatory bias in splenic Ly6Chigh monocytes, which showed predominantly upregulated expression of IFN-γ responsive genes after MI. Our results indicate that conventional CD4+ T-cells promote and Tregs attenuate splenic myelopoiesis and proinflammatory differentiation of monocytes.

Human-like Response of Pig T Cells to Superagonistic Anti-CD28 Monoclonal Antibodies.

Because of its size, anatomical similarities, and now also accessibility to genetic manipulations, pigs are used as animal models for human diseases and immune system development. However, expression and function of CD28, the most important costimulatory receptor expressed by T cells, so far is poorly understood in this species. Using a newly generated mAb (mAb 3D11) with specificity for pig CD28, we detected CD28 on CD8+ and CD4+ αß T cells. Among γδ T cells, CD28 expression was restricted to a small CD2+ subpopulation of phenotypically naive cells. Functionally, CD28 ligation with mAb 3D11-costimulated porcine T cells, enhanced proliferation and cytokine secretion in vitro. We used a second, likewise newly generated but superagonistic, anti-CD28 mAb (CD28-SA; mAb 4D12) to test the function of CD28 on porcine T cells in a pilot study in vivo. Injection of the CD28-SA into pigs in vivo showed a very similar dose-response relationship as in humans (i.e., 100 µg/kg body weight [BW]) of CD28-SA induced a cytokine release syndrome that was avoided at a dose of 10 µg/kg BW and below. The data further suggest that low-dose (10 µg/kg BW) CD28-SA infusion was sufficient to increase the proportion of Foxp3+ regulatory T cells among CD4+ T cells in vivo. The pig is thus a suitable animal model for testing novel immunotherapeutics. Moreover, data from our pilot study in pigs further suggest that low-dose CD28-SA infusion might allow for selective expansion of CD4+ regulatory T cells in humans.

Tumor necrosis factor-α links heat and inflammation with Fabry pain.

Fabry disease (FD) is an X-linked lysosomal storage disorder associated with pain triggered by heat or febrile infections. We modelled this condition by measuring the cytokine expression of peripheral blood mononuclear cells (PBMC) from FD patients in vitro upon stimulation with heat and lipopolysaccharide (LPS). We enrolled 67 FD patients and 37 healthy controls. We isolated PBMC, assessed their gene expression of selected pro- and anti-inflammatory cytokines, incubated them with heat, LPS, globotriaosylceramide (Gb3), and tumor necrosis factor-α (TNF), and measured TNF secretion in the supernatant and intracellular Gb3 accumulation, respectively. We found increased TNF, interleukin (IL-)1ß, and toll-like receptor 4 (TLR4) gene expression in FD men (p < .05 to p < .01). TNF and IL-10 were higher, and IL-4 was lower in the subgroup of FD men with pain compared to controls (p < .05 to p < .01). Hereby, TNF was only increased in FD men with pain and classical mutations (p < .05) compared to those without pain. PBMC from FD patients secreted more TNF upon stimulation with LPS (p < .01) than control PBMC. Incubation with Gb3 and an additional α-galactosidase A inhibitor did not further increase TNF secretion, but incubation with TNF greatly increased the Gb3 load in FD PBMC compared to controls (p < .01). Also, LPS incubation and heat challenge (40 °C) increased Gb3 accumulation in PBMC of patients compared to baseline (p < .05 each), while no alterations were observed in control PBMC. Our data show that TNF holds a crucial role in the pathophysiology of FD associated pain, which may open a novel perspective for analgesic treatment in FD pain.