skip to main content

Title: Droplet encapsulation improves accuracy of immune cell cytokine capture assays
Quantification of cell-secreted molecules, e.g. , cytokines, is fundamental to the characterization of immune responses. Cytokine capture assays that use engineered antibodies to anchor the secreted molecules to the secreting cells are widely used to characterize immune responses because they allow both sensitive identification and recovery of viable responding cells. However, if the cytokines diffuse away from the secreting cells, non-secreting cells will also be identified as responding cells. Here we encapsulate immune cells in microfluidic droplets and perform in-droplet cytokine capture assays to limit the diffusion of the secreted cytokines. We use microfluidic devices to rapidly encapsulate single natural killer NK-92 MI cells and their target K562 cells into microfluidic droplets. We perform in-droplet IFN-γ capture assays and demonstrate that NK-92 MI cells recognize target cells within droplets and become activated to secrete IFN-γ. Droplet encapsulation prevents diffusion of secreted products to neighboring cells and dramatically reduces both false positives and false negatives, relative to assays performed without droplets. In a sample containing 1% true positives, encapsulation reduces, from 94% to 2%, the number of true-positive cells appearing as negatives; in a sample containing 50% true positives, the number of non-stimulated cells appearing as positives is reduced from 98% to 1%. After cells are released from the droplets, secreted cytokine remains captured onto secreting immune cells, enabling FACS-isolation of populations highly enriched for activated effector immune cells. Droplet encapsulation can be used to reduce background and improve detection of any single-cell secretion assay.  more » « less
Award ID(s):
1708729 1420570
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Lab on a Chip
Page Range / eLocation ID:
1513 to 1520
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Cytokine‐induced memory‐like (CIML) NK cells are endowed with the capacity to mediate enhanced effector functions upon cytokine or activating receptor restimulation for several weeks following short‐term preactivation with IL‐12, IL‐15, and IL‐18. Promising results from a first‐in‐human clinical trial highlighted the clinical potential of CIML NK cells as adoptive immunotherapy for patients with hematologic malignancies. However, the mechanisms underlying CIML NK cell differentiation and increased functionality remain incompletely understood. Semaphorin 7A (SEMA7A) is a potent immunomodulator expressed in activated lymphocytes and myeloid cells. In this study, we show that SEMA7A is substantially upregulated on NK cells stimulated with cytokines, and specifically marks activated NK cells with a strong potential to release IFN‐γ. In particular, preactivation of NK cells with IL‐12+IL‐15+IL‐18 resulted in greater than tenfold upregulation of SEMA7A and enhanced expression of the ligand for SEMA7A, integrin‐β1, on CIML NK cells. Strikingly, preactivation in the presence of antibodies targeting SEMA7A lead to significantly decreased IFN‐γ production following restimulation. These results imply a novel mechanism by which cytokine‐enhanced SEMA7A/integrin‐β1 interaction promotes CIML NK cell differentiation and maintenance of increased functionality. Our data suggest that targeting SEMA7A/integrin‐β1 signaling might provide a novel immunotherapeutic approach to potentiate antitumor activity of CIML NK cells.

    more » « less
  2. Abstract

    Integrated microfluidic cellular phenotyping platforms provide a promising means of studying a variety of inflammatory diseases mediated by cell‐secreted cytokines. However, immunosensors integrated in previous microfluidic platforms lack the sensitivity to detect small signals in the cellular secretion of proinflammatory cytokines with high precision. This limitation prohibits researchers from studying cells secreting cytokines at low abundance or existing at a small population. Herein, the authors present an integrated platform named the “digital Phenoplate (dPP),” which integrates digital immunosensors into a microfluidic chip with on‐chip cell assay chambers, and demonstrates ultrasensitive cellular cytokine secretory profile measurement. The integrated sensors yield a limit of detection as small as 0.25 pg mL−1for mouse tumor necrosis factor alpha (TNF‐α). Each on‐chip cell assay chamber confines cells whose population ranges from ≈20 to 600 in arrayed single‐cell trapping microwells. Together, these microfluidic features of the dPP simultaneously permit precise counting and image‐based cytometry of individual cells while performing parallel measurements of TNF‐α released from rare cells under multiple stimulant conditions for multiple samples. The dPP platform is broadly applicable to the characterization of cellular phenotypes demanding high precision and high throughput.

    more » « less
  3. null (Ed.)
    A multifunctional microfluidic platform combining on-demand aqueous-phase droplet generation, multi-droplet storage, and controlled merging of droplets selected from a storage library in a single integrated microfluidic device is described. A unique aspect of the technology is a microfluidic trap design comprising a droplet trap chamber and lateral bypass channels integrated with a microvalve that supports the capture and merger of multiple droplets over a wide range of individual droplet sizes. A storage unit comprising an array of microfluidic traps operates in a first-in first-out manner, allowing droplets stored within the library to be analyzed before sequentially delivering selected droplets to a downstream merging zone, while shunting other droplets to waste. Performance of the microfluidic trap is investigated for variations in bypass/chamber hydrodynamic resistance ratio, micro-chamber geometry, trapped droplet volume, and overall flow rate. The integrated microfluidic platform is then utilized to demonstrate the operational steps necessary for cell-based assays requiring the isolation of defined cell populations with single cell resolution, including encapsulation of individual cells within an aqueous-phase droplet carrier, screening or incubation of the immobilized cell-encapsulated droplets, and generation of controlled combinations of individual cells through the sequential droplet merging process. Beyond its utility for cell analysis, the presented platform represents a versatile approach to robust droplet generation, storage, and merging for use in a wide range of droplet-based microfluidics applications. 
    more » « less
  4. Abstract

    In this invited article, we explain technical aspects of the lymphocytic choriomeningitis virus (LCMV) system, providing an update of a prior contribution by Matthias von Herrath and J. Lindsay Whitton. We provide an explanation of the LCMV infection models, highlighting the importance of selecting an appropriate route and viral strain. We also describe how to quantify virus‐specific immune responses, followed by an explanation of useful transgenic systems. Specifically, our article will focus on the following protocols. © 2020 Wiley Periodicals LLC.

    Basic Protocol 1: LCMV infection routes in mice

    Support Protocol 1: Preparation of LCMV stocks


    Support Protocol 2: Plaque assay

    Support Protocol 3: Immunofluorescence focus assay (IFA) to measure LCMV titer


    Basic Protocol 2: Triple tetramer staining for detection of LCMV‐specific CD8 T cells

    Basic Protocol 3: Intracellular cytokine staining (ICS) for detection of LCMV‐specific T cells

    Basic Protocol 4: Enumeration of direct ex vivo LCMV‐specific antibody‐secreting cells (ASC)

    Basic Protocol 5: Limiting dilution assay (LDA) for detection of LCMV‐specific memory B cells

    Basic Protocol 6: ELISA for quantification of LCMV‐specific IgG antibody

    Support Protocol 4: Preparation of splenic lymphocytes

    Support Protocol 5: Making BHK21‐LCMV lysate

    Basic Protocol 7: Challenge models


    Basic Protocol 8: Transfer of P14 cells to interrogate the role of IFN‐I on CD8 T cell responses

    Basic Protocol 9: Comparing the expansion of naïve versus memory CD4 T cells following chronic viral challenge

    more » « less
  5. null (Ed.)
    Currently, there is a great interest in nanoparticle-based vaccine delivery. Recent studies suggest that nanoparticles when introduced into the biological milieu are not simply passive carriers but may also contribute immunological activity themselves or of their own accord. For example there is considerable interest in the biomedical applications of one of the physiologically-based inorganic metal oxide nanoparticle, zinc oxide (ZnO). Indeed zinc oxide (ZnO) NP are now recognized as a nanoscale chemotherapeutic or anticancer nanoparticle (ANP) and several recent reports suggest ZnO NP and/or its complexes with drug and RNA induce a potent antitumor response in immuno-competent mouse models. A variety of cell culture studies have shown that ZnO NP can induce cytokines such as IFN-γ, TNF-α, IL-2, and IL-12 which are known to regulate the tumor microenvironment. Much less work has been done on magnesium oxide (MgO), cobalt oxide (Co3O4), or nickel oxide (NiO); however, despite the fact that these physiologically-based metal oxide NP are reported to functionally load and assemble RNA and protein onto their surface and may thus also be of potential interest as nanovaccine platform. Here we initially compared in vitro immunogenicity of ZnO and Co3O4 NP and their effects on cancer-associated or tolerogenic cytokines. Based on these data we moved ZnO NP forward to testing in the ex vivo splenocyte assay relative to MgO and NiO NP and these data showed significant difference for flow cytometry sorted population for ZnO-NP, relative to NiO and MgO. These data suggesting both molecular and cellular immunogenic activity, a double-stranded anticancer RNA (ACR), polyinosinic:poly cytidylic acid (poly I:C) known to bind ZnO NP; when ZnO-poly I:C was injected into B16F10-BALB/C tumor significantly induced, IL-2 and IL-12 as shown by Cohen’s d test. LL37 is an anticancer peptide (ACP) currently in clinical trials as an intratumoral immuno-therapeutic agent against metastatic melanoma. LL37 is known to bind poly I:C where it is thought to compete for receptor binding on the surface of some immune cells, metastatic melanoma and lung cells. Molecular dynamic simulations revealed association of LL37 onto ZnO NP confirmed by gel shift assay. Thus using the well-characterized model human lung cancer model cell line (BEAS-2B), poly I:C RNA, LL37 peptide, or LL37-poly I:C complexes were loaded onto ZnO NP and delivered to BEAS-2B lung cells, and the effect on the main cancer regulating cytokine, IL-6 determined by ELISA. Surprisingly ZnO-LL37, but not ZnO-poly I:C or the more novel tricomplex (ZnO-LL37-poly I:C) significantly suppressed IL-6 by >98–99%. These data support the further evaluation of physiological metal oxide compositions, so-called physiometacomposite (PMC) materials and their formulation with anticancer peptide (ACP) and/or anticancer RNA (ACR) as a potential new class of immuno-therapeutic against melanoma and potentially lung carcinoma or other cancers. 
    more » « less