Label-Free Identification of White Blood Cells Using Machine Learning.

White blood cell (WBC) differential counting is an established clinical routine to assess patient immune system status. Fluorescent markers and a flow cytometer are required for the current state-of-the-art method for determining WBC differential counts. However, this process requires several sample preparation steps and may adversely disturb the cells. We present a novel label-free approach using an imaging flow cytometer and machine learning algorithms, where live, unstained WBCs were classified. It achieved an average F1-score of 97% and two subtypes of WBCs, B and T lymphocytes, were distinguished from each other with an average F1-score of 78%, a task previously considered impossible for unlabeled samples. We provide an open-source workflow to carry out the procedure. We validated the WBC analysis with unstained samples from 85 donors. The presented method enables robust and highly accurate identification of WBCs, minimizing the disturbance to the cells and leaving marker channels free to answer other biological questions. It also opens the door to employing machine learning for liquid biopsy, here, using the rich information in cell morphology for a wide range of diagnostics of primary blood. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Monocytes give rise to mucosal, but not splenic, conventional dendritic cells.

The mononuclear phagocyte (MP) system is a body-wide macrophage (MPhi) and dendritic cell (DC) network, which contributes to tissue homeostasis, inflammation, and immune defense. The in vivo origins of MPs remain poorly understood. Here, we use an adoptive precursor cell transfer strategy into MP-depleted mice to establish the in vivo differentiation sequence from a recently identified MPhi/DC-restricted bone marrow (BM) precursor (MDP) via BM and blood intermediates to peripheral MPhis and DCs. We show that MDPs are in vivo precursors of BM and blood monocytes. Interestingly, grafted Gr1high "inflammatory" blood monocytes shuttle back to the BM in the absence of inflammation, convert into Gr1low monocytes, and contribute further to MP generation. The grafted monocytes give rise to DCs in the intestinal lamina propria and lung, but not to conventional CD11chigh DCs in the spleen, which develop during homeostasis from MDPs without a monocytic intermediate.

p11 regulates extracellular plasmin production and invasiveness of HT1080 fibrosarcoma cells.

The defining characteristic of a tumor cell is its ability to escape the constraints imposed by neighboring cells, invade the surrounding tissue, and metastasize to distant sites. This invasive property of tumor cells is dependent on activation of proteases at the cell surface. Most cancer cells secrete the urokinase-type plasminogen activator, which converts cell-bound plasminogen to plasmin. Here we address the issue of whether the plasminogen binding protein, p11, plays a significant role in this process. Transfection of human HT1080 fibrosarcoma cells with the human p11 gene in the antisense orientation resulted in a loss of p11 protein from the cell surface and concomitant decreases in cellular plasmin production, ECM degradation, and cellular invasiveness. The transfected cells demonstrated reduced development of lung metastatic foci in SCID mice. In contrast, HT1080 cells transfected with the p11 gene in the sense orientation displayed increased cell surface p11 protein and concomitant increases in cellular plasmin production, as well as enhanced ECM degradation and enhanced cellular invasiveness. The p11 overexpressing cells showed enhanced development of lung metastatic foci. These data establish that changes in the extracellular expression of the plasminogen receptor protein, p11, dramatically affect tumor cell-mediated pericellular proteolysis.

A novel image-based quantitative method for the characterization of NETosis.

NETosis is a newly recognized mechanism of programmed neutrophil death. It is characterized by a stepwise progression of chromatin decondensation, membrane rupture, and release of bactericidal DNA-based structures called neutrophil extracellular traps (NETs). Conventional 'suicidal' NETosis has been described in pathogenic models of systemic autoimmune disorders. Recent in vivo studies suggest that a process of 'vital' NETosis also exists, in which chromatin is condensed and membrane integrity is preserved. Techniques to assess 'suicidal' or 'vital' NET formation in a specific, quantitative, rapid and semiautomated way have been lacking, hindering the characterization of this process. Here we have developed a new method to simultaneously assess both 'suicidal' and 'vital' NETosis, using high-speed multi-spectral imaging coupled to morphometric image analysis, to quantify spontaneous NET formation observed ex-vivo or stimulus-induced NET formation triggered in vitro. The use of imaging flow cytometry allows automated, quantitative and rapid analysis of subcellular morphology and texture, and introduces the potential for further investigation using NETosis as a biomarker in pre-clinical and clinical studies.

CX3CR1+ CD115+ CD135+ common macrophage/DC precursors and the role of CX3CR1 in their response to inflammation.

CX(3)CR1 expression is associated with the commitment of CSF-1R(+) myeloid precursors to the macrophage/dendritic cell (DC) lineage. However, the relationship of the CSF-1R(+) CX(3)CR1(+) macrophage/DC precursor (MDP) with other DC precursors and the role of CX(3)CR1 in macrophage and DC development remain unclear. We show that MDPs give rise to conventional DCs (cDCs), plasmacytoid DCs (PDCs), and monocytes, including Gr1(+) inflammatory monocytes that differentiate into TipDCs during infection. CX(3)CR1 deficiency selectively impairs the recruitment of blood Gr1(+) monocytes in the spleen after transfer and during acute Listeria monocytogenes infection but does not affect the development of monocytes, cDCs, and PDCs.

A clonogenic bone marrow progenitor specific for macrophages and dendritic cells.

Macrophages and dendritic cells (DCs) are crucial for immune and inflammatory responses and belong to a network of cells that has been termed the mononuclear phagocyte system (MPS). However, the origin and lineage of these cells remain poorly understood. Here, we describe the isolation and clonal analysis of a mouse bone marrow progenitor that is specific for monocytes, several macrophage subsets, and resident spleen DCs in vivo. It was also possible to recapitulate this differentiation in vitro by using treatment with the cytokines macrophage colony-stimulating factor and granulocyte-macrophage colony-stimulating factor. Thus, macrophages and DCs appear to renew from a common progenitor, providing a cellular and molecular basis for the concept of the MPS.

RNA interference-mediated silencing of the S100A10 gene attenuates plasmin generation and invasiveness of Colo 222 colorectal cancer cells.

S100A10 is a key plasminogen receptor of the extracellular cell surface that is overexpressed in many cancer cells. Typically, S100A10 is thought to be anchored to the plasma membrane via the phospholipid-binding sites of its binding partner, annexin A2. Here, using the potent and highly sequence-specific mechanism of RNA interference (RNAi), we have stably silenced the expression of the S100A10 gene in colorectal (CCL-222) cancer cells. We show that siRNA expression mediated by the pSUPER vector causes efficient, stable, and specific down-regulation of S100A10 gene expression. The siRNA-mediated down-regulation of S100A10 gene expression resulted in a major decrease in the appearance of extracellular S100A10 protein and correlated with a 45% loss of plasminogen binding, a 65% loss in cellular plasmin generation and a complete loss in plasminogen-dependent cellular invasiveness. We also observed that the CCL-222 cells do not express annexin A2 on their extracellular surface. Thus, the data show that annexin A2 is not required by S100A10 for its association with the plasma membrane, for its colocalization with uPAR, or for its binding and activation of plasminogen.

The p11 subunit of annexin II heterotetramer is regulated by basic carboxypeptidase.

The Ca(2+)-dependent phospholipid-binding protein annexin II heterotetramer (AIIt) is composed of two copies of annexin II and a p11 dimer. The interaction of the carboxyl-terminal lysine residues of the p11 subunit of AIIt with the lysine-binding kringle domains of plasminogen is believed to play a key role in plasminogen binding and stimulation of the tPA-catalyzed cleavage of plasminogen to plasmin. In the current report, we show that AIIt-stimulated plasminogen activation is regulated by basic carboxypeptidases, in vitro. The incubation of AIIt with a 1/400 molar ratio of carboxypeptidase B for periods as short as 2 min resulted in a significant loss in AIIt-stimulated plasminogen activation. Carboxypeptidase B (CpB) as well as thrombin-activated fibrinolysis inhibitor (TAFIa) and carboxypeptidase N (CpN) rapidly reduced AIIt-stimulated plasminogen activation by 80%. The molar ratio of carboxypeptidase/AIIt for half-maximal inhibition of AIIt was 1/4700, 1/700, and 1/500 for CpB, TAFIa, and CpN, respectively. Treatment of AIIt with carboxypeptidase resulted in loss of both carboxyl-terminal lysine residues from the p11 subunit, which correlated with a decrease in the k(cat) and an increase in the K(m) for plasminogen activation. The data reveal a novel mechanism for the regulation of AIIt-stimulated plasminogen activation.