How single-cell immunology is benefiting from microfluidic technologies

Abstract

The immune system is a complex network of specialized cells that work in concert to protect against invading pathogens and tissue damage. Imbalances in this network often result in excessive or absent immune responses leading to allergies, autoimmune diseases, and cancer. Many of the mechanisms and their regulation remain poorly understood. Immune cells are highly diverse, and an immune response is the result of a large number of molecular and cellular interactions both in time and space. Conventional bulk methods are often prone to miss important details by returning population-averaged results. There is a need in immunology to measure single cells and to study the dynamic interplay of immune cells with their environment. Advances in the fields of microsystems and microengineering gave rise to the field of microfluidics and its application to biology. Microfluidic systems enable the precise control of small volumes in the femto-to nanoliter range. By controlling device geometries, surface chemistry, and flow behavior, microfluidics can create a precisely defined microenvironment for single-cell studies with spatiotemporal control. These features are highly desirable for single-cell analysis and have made microfluidic devices useful tools for studying complex immune systems. In addition, microfluidic devices can achieve high-throughput measurements, enabling in-depth studies of complex systems. Microfluidics has been used in a large panel of biological applications, ranging from single-cell genomics, cell signaling and dynamics to cell-cell interaction and cell migration studies. In this review, we give an overview of state-of-the-art microfluidic techniques, their application to single-cell immunology, their advantages and drawbacks, and provide an outlook for the future of single-cell technologies in research and medicine.

Single-Cell Technologies for the Study of Antibody-Secreting Cells

“…The topic of techniques for measuring single-cell protein secretion in immunology and their origins have been previously described (14,15). Three general strategies are available for characterizing the secreted effectors of immune cells, each with applicability to ASC: spot-based assays, cytometry-based assays, and microfluidic-assays.…”

“…Microfluidic single cell assays essentially miniaturize existing techniques to assess ASC secretions, to increase the scale and throughput of analyses and enable single cell resolution via compartmentalization into either wells or droplets (14,15). Miniaturization also allows for greatly reduced reagent usage and less cells are needed per experiment.…”

Single Cell RNA Sequencing in Autoimmune Inflammatory Rheumatic Diseases: Current Applications, Challenges and a Step Toward Precision Medicine

“…Microfluidic devices, on the other hand, can be used for both: to capture each individual cell into one compartment/reaction unit, either a microwell or a microdroplet, as well as to perform downstream, highly standardized and automated reactions directly in every unit ( 22 , 23 ). Microdroplet technology (i.e., 10x Genomics Chromium) encapsulates each aqueous droplet in a continuous oil phase which contains an individual cell mixed with gel beads with uniquely barcoded set of oligonucleotides, called unique molecular identifiers (UMIs).…”

Microfluidic Compartmentalization Platforms for Single Cell Analysis

“…The compartmentalization of single cells in small volumes can drastically improve the signal-to-noise ratio by reducing background noise, where it would be challenging to acquire the signal of individual cells from a bulk population [ 17 , 18 ]. The capabilities in multiplexing and parallelization are also unique characteristics in microfluidic systems that make them suitable for single-cell analysis [ 19 , 20 ].…”