Figure 1: Histamine and Clobenpropit inhibit purified HIV-stimulated pDC activation.

(a) pDC were acquired by flow cytometry before and after purification from PBMC of healthy donors. Negative selection was used to obtain purity higher than 90% in all experiments. (b) Chemical structures of histamine (HA) and clobenpropit (CB). (c) Isolated pDC were pretreated with histamine or with CB at the concentration of 10 μM and then stimulated with microvesicles (mock) alone or with HIV overnight. IFN-α was measured in the supernatants by Elisa. (d) IFN-α production overtime was measured in supernatants of purified pDC cultured overnight with microvesicles (mock) alone or with HIV alone or together with CB at the concentration of 10 μM. (e) Levels of membrane TRAIL were assessed by flow cytometry on purified pDC after pre-incubation with CB or the specific TLR7 antagonist, A151, and then overnight HIV stimulation. (f) mRNA levels of TRAIL from purified pDC pre-incubated with CB (10 μM) and stimulated overnight with HIV, were measured by RT-qPCR and normalized to RPL13A. Production of IFN-α by Elisa in supernatants (g) or expression of membrane TRAIL at the surface of the cells by flow cytometry (h) from purified pDC pre-incubated with CB and then cultured overnight with Influenza A or Dengue viruses. Inhibition of IFN-α production (i) and inhibition of TRAIL expression (j) were assessed in supernatants of PBMC and by flow cytometry on PBMC cultured overnight with Influenza A virus alone or together with histamine (HA) or CB at a concentration ranging from 0.5 μM to 1 mM. Data shown as the mean of three independent experiments ±s.e.m. P values (p) were determined using a two-tailed Student’s t test. ***P<0.001, **P<0.01, *P<0.05.