The evidence of PMD in MCs interacting with Tregs could be in agreement with the earlier observation that Tregs impair FcεRI-mediated degranulation without affecting IL-6 and TNF-α production 4. To further confirm the selective effect of Tregs on degranulation, different MC granule-associated mediators

were measured. As shown in Fig. 6A, Tregs significantly inhibited the secretion of mediators such as histamine and leukotrienes that are usually released immediately after activation and peaked within a few minutes. On the other hand, the amount of several cytokines, chemokines and growth factors released by MCs 24 h after Ag challenge was not significantly modified by the presence of WT or OX40-deficient Tregs (Fig. 6A). As expected, the loss of OX40 expression on Tregs selectively impaired their ability to inhibit selleck chemical the secretion of early released MC mediators. To assess the timing of Treg-mediated inhibition, we looked at the kinetics of TNF-α release, as

this cytokine is rapidly released from preformed stores and is followed by the subsequent release of large quantities of the newly synthesized cytokine upon IgE-dependent MC activation 25. As shown in Fig. 6B, the amount of released TNF-α 15 and 30 min after Ag addition was reduced when MCs were incubated with Tregs, but no differences were detected at 1 and 12 h, indicating that the lower level of detected TNF-α in early time points could be due to a delay in secretion rather than an effective inhibition. This suggests a time-dependent effect of Treg inhibition. To develop an effective immune response, the cells of the X-396 immune system must communicate through secretion of mediators and direct cell–cell interactions. One morphological paradigm of the close connection between the T cell and the antigen-presenting cell is the immunological synapse, whose structure relies on cell–cell contact through T cell membrane-bound receptors. The consequences of immunological synapse formation are bi-directional signaling that modulates cellular effector functions 26. MCs express several

co-stimulatory molecules 6-phosphogluconolactonase on the cell membrane that confers the ability to physically interact with other cells of the immune system 10. The group of Espinosa provided the first morphological evidence of immunological synapse formation between MCs and T cells resulting in MC and T cell activation 27. More recently, a functional complex between MCs and eosinophils, triggered upon receptor–ligand binding, has been described 6. Both MCs and eosinophils engaged in this complex undergo shape changes that might be the result of their physical interaction through membrane adhesion molecules as well as reciprocal modulation of mediators and enzymes released 6. The concept that MCs and Tregs functionally interact has been put forward by multiple recent reports 4, 5; however, as MC heterogeneity is widely documented 21 this variability should be considered in the investigation of such interactions.