Plasmacytoid dendritic cells (pDCs) are the professional type I interferon (IFN)-producing cells, and upon activation they traffic to lymph organs, where they bridge innate and adaptive immunity. Using multianalyte profiling (MAP), we have mapped the key chemokines and cytokines produced in response to pDC activation, taking into consideration the role of autocrine IFN, as well as paracrine effects on other innate cells (e.g., monocytes and conventional DCs). Interestingly, we identify four distinct cytokine/chemokine loops initiated by Toll-like receptor engagement. Finally, we applied this analytic approach to the study of pDC activity in chronic hepatitis C patients. Based on the activation state of pDCs in fresh blood, the lack of agonistic activity of infectious virions, the production of a broad array of cytokines/chemokines once stimulated, and the direct effects of pDCs on other PBMCs, we conclude that the pDCs from hepatitis C virus (HCV)-infected individuals are fully functional and are, indeed, a viable drug target. In sum, this study provides insight into the use of MAP technology for characterizing cytokine networks, and highlights how a rare cell type integrates the activation of other inflammatory cells. Furthermore, this work will help evaluate the therapeutic application of pDC agonists in diseases such as chronic HCV infection.

PB HPC quantification is very useful to quickly determine the initiation of PBPC apheresis especially for patients with higher concentrations. For patients exhibiting a lower HPC count (<5 x 10(6)/L), other parameters such as a CD34 test may be needed. Such a policy associated with a length of apheresis adapted to the richness in the PB CD34+ cells allows for optimizing the organization of centers with an improvement in patient comfort and economical savings.

Successful peripheral blood stem cell (PBSC) collection depends on the timing of apheresis based on CD34+ cell enumeration. Because this analysis is expensive and induces organization difficulties, we evaluated hematopoietic progenitor cell (HPC) quantification on the Sysmex XE-2100 as a surrogate analysis. We tested 157 blood samples for CD34+ cells and HPC counts. We found a good linear correlation between HPC and CD34+ and determined simple rules allowing to use HPC count in daily practice. We set a positive cut-off >30 HPC/mm(3) for allowing PBSC harvest and a negative cut-off at 0 HPC/mm(3) for which collection should be delayed. These two situations accounted for 62% of cases and CD34+ cell count by flow cytometry confirmed HPC result in 95% of cases. Between 0 and 30 HPC/mm3, CD34+ enumeration is required for decision-making. We conclude that HPC count may be a useful surrogate for CD34+ enumeration in PBSC harvest monitoring.