The fate of hematopoietic stem and progenitor cells (HSPCs) is regulated by their interaction with stromal cells in the bone marrow. However, the cellular mechanisms regulating HSPC interaction with these cells and their potential impact on HSPC polarity are still poorly understood. Here we evaluated the impact of cell-cell contacts with osteoblasts or endothelial cells on the polarity of HSPC. We found that an HSPC can form a discrete contact site that leads to the extensive polarization of its cytoskeleton architecture. Notably, the centrosome was located in proximity to the contact site. The capacity of HSPCs to polarize in contact with stromal cells of the bone marrow appeared to be specific, as it was not observed in primary lymphoid or myeloid cells or in HSPCs in contact with skin fibroblasts. The receptors ICAM, VCAM, and SDF1 were identified in the polarizing contact. Only SDF1 was independently capable of inducing the polarization of the centrosome-microtubule network.
© 2021 Bessy et al.

DotScan antibody microarrays were initially developed for the extensive surface profiling of live leukemia and lymphoma cells. DotScan's diagnostic capability was validated with an extensive clinical trial using mononuclear cells from the blood or bone marrow of leukemia or lymphoma patients. DotScan has also been used for the profiling of surface proteins on peripheral blood mononuclear cells (PBMC) from patients with HIV, liver disease, and stable and progressive B-cell chronic lymphocytic leukemia (CLL). Fluorescence multiplexing allowed the simultaneous profiling of cancer cells and leukocytes from disaggregated colorectal and melanoma tumor biopsies after capture on DotScan. In this chapter, we have used DotScan for the surface profiling of extracellular vesicles (EV) recovered from conditioned growth medium of cancer cell lines and the blood of patients with CLL. The detection of captured EV was performed by enhanced chemiluminescence (ECL) using biotinylated antibodies that recognized antigens expressed on the surface of the EV subset of interest. DotScan was also used to profile EV from the blood of healthy individuals and the ascites fluid of ovarian cancer patients. DotScan binding patterns of EV from human plasma and other body fluids may yield diagnostic or prognostic signatures for monitoring the incidence, treatment, and progression of cancers.

We previously demonstrated that the biguanide-based compound NB325 inhibits human immunodeficiency virus type 1 (HIV-1) infection by interacting with the CXCR4 viral coreceptor. This interaction also appeared to be persistent, since HIV-1 infection was inhibited even when the virus was introduced subsequent to the removal of NB325 from the cell culture medium. The present studies were conducted to determine the extent and mechanism of this prolonged antiviral activity. Persistent inhibition of HIV-1 infection by NB325 was concentration dependent and was apparent up to 8 h after removal of the compound. Flow cytometric analyses of stimulated CD4(+) T lymphocytes exposed to NB325 demonstrated concentration-dependent reductions in CXCR4 extracellular loop 2 epitope recognition that were maintained up to 24 h after removal of the compound. CXCL12-induced chemotaxis was also persistently inhibited following pre-exposure to NB325. These results demonstrate that persistent inhibition of X4 HIV-1 infection by NB325 involves extended perturbation of the viral coreceptor CXCR4.