Mass Cytometry, Imaging Mass Cytometry, and Multiplexed Ion Beam Imaging Use in a Clinical Setting

Key points

Introduction

Flow cytometry (FC) is a widely used tool in basic and clinical research with its ability to study malignancies, infectious diseases, and immune system function. Its utility is due to its ability, at a single-cell level, to detect any component recognized by an antibody. This utility, however, is constrained by the number of parameters that can be analyzed simultaneously. Most clinical flow cytometers can analyze between 4 and 15 parameters, this limitation is primarily due to fluorescent reporters and their spectral emission overlap. Recent advancements are overcoming this limitation such as multispectral flow cytometers that can recognize approximately 32 different parameters ¹ ; however, one of the most significant developments is mass cytometry (MC), and MC-based imaging. 234567

In principle, MC is similar to FC, as both use antibody-based detection at a single-cell level and generate similar data. The difference is that MC uses metal-tagged antibodies instead of fluorescently labeled antibodies. The cells, with the bound antibody-metal conjugates, are detected through time of flight mass spectrometry (TOF MS). TOF MS is able to distinguish ions of different atomic weights with less than 0.5% spillover into adjacent channels, yielding a high resolution that allows for a large increase in measurable parameters of the MC system. It is now considered routine to have panels of approximately 50 antibodies and up to 60 total measured ions, and this number is continuing to increase, with recent of additions of metals such as nanoparticle-tantalum–based antibody conjugation. ⁸ The theoretic upper limit of parameters is approximately 120 mass channels, which may be reached as the field continues to advance. Although MC has been a significant development, the application of metal-conjugated antibodies and TOF detection has continued to develop with imaging MC (IMC) and multiplexed ion beam imaging (MIBI). 456 ^, 9 IMC and MIBI both perform the same function of allowing very high-parameter detection of antibody binding to tissues, but the systems work in different ways. All 3 systems can enable very high-dimensional characterization of both surface antigens (to define cell identity), as well as intracellular antigens that can be used to characterize cellular functional properties.