Detection of Immune Checkpoint Receptors – A Current Challenge in Clinical Flow Cytometry

Abstract

Immunological therapy principles are increasingly determining modern medicine. They are used to treat diseases of the immune system, for tumors, but also for infections, neurological diseases, and many others. Most of these therapies base on antibodies, but small molecules, soluble receptors or cells and modified cells are also used. The development of immune checkpoint inhibitors is amazingly fast. T-cell directed antibody therapies against PD-1 or CTLA-4 are already firmly established in the clinic. Further targets are constantly being added and it is becoming increasingly clear that their expression is not only relevant on T cells. Furthermore, we do not yet have any experience with the long-term systemic effects of the treatment. Flow cytometry can be used for diagnosis, monitoring, and detection of side effects. In this review, we focus on checkpoint molecules as target molecules and functional markers of cells of the innate and acquired immune system. However, for most of the interesting and potentially relevant parameters, there are still no test kits suitable for routine use. Here we give an overview of the detection of checkpoint molecules on immune cells in the peripheral blood and show examples of a possible design of antibody panels.

Development of a Flow Cytometry Assay to Predict Immune Checkpoint Blockade-Related Complications

“…This assay is a refinement of methods used previously to develop a predictive model for hepatitis following combined αPD-1/αCTLA-4. Specifically, we adapted the assay design to include measurements of monocyte subsets together with CD279 + CD8 + T cells, which may be useful parameters for predicting treatment-related hepatitis, clinical response to therapy or tumor staging ( 48 , 49 ).…”

Comparison of Laboratory Methods for the Clinical Follow Up of Checkpoint Blockade Therapies in Leukemia: Current Status and Challenges Ahead

“…Only, there is a need for ready-to-use individual testing kits with reasonable prices that can be adapted to clinical laboratories from clinical trials. As mentioned by other authors, lack of “Conformite Europeenne” (CE) or “ In Vitro Diagnostics” (IVD) labels for the reagents to be used in detection ICs and their counterparts requires more standardization and acceptance of the methods used for the standardization by clinical laboratories that are normally required to use the CE or IVD labeled products only ( 90 ). Extensive non-CE and non-IVD panels suggested by the same authors should be evaluated by more laboratories, as the clones chosen for this type of analysis may be different in laboratories, standardization suggestions are cumbersome and challenging with many variations in the measurement systems, reagents, preparation, and analysis methods.…”

On Demand Biosensors for Early Diagnosis of Cancer and Immune Checkpoints Blockade Therapy Monitoring from Liquid Biopsy

“…These immune checkpoints can be detected on tumor cells and in the tumor microenvironment (TME) through traditional tissue biopsies and IHC as well as via biosensors. Although these biomarkers are potentially for the detection of cancer, the developmental status of biosensors designed to detect these immune checkpoint markers is still at an early stage [ 55 ]. In this article, we will focus upon several such soluble immune checkpoints-sPD-1, sPD-L1, sLAG-3, and sTIM-3-that are expressed on peripheral blood mononuclear cells that could potentially be diagnosed through biosensors.…”