Standardizing immunophenotyping for the Human Immunology Project

Key Points Standardized immunophenotyping assays are a requisite for accomplishing the proposed Human Immunology Project, which involves the comprehensive elucidation of the metrics of healthy versus diseased or perturbed human immune systems. The variables inherent in flow cytometry immunophenotyping are largely known, and include reagent choice, sample handling, instrument setup and data analysis; strategies to mitigate each of these variables are available. Several groups, including the Human Immunophenotyping Consortium, are standardizing reagent panels for flow cytometry. Together with the adoption of such standard panels, an infrastructure for aggregating and mining results will be needed. Availability of such panels and the data-mining infrastructure should result in more rapid biomarker discovery for immunologically relevant diseases. The authors use flow cytometry of peripheral blood mononuclear cells as an example to outline the approaches to assay standardization that will be required to realize the full potential of immunophenotyping as a research tool and in the clinic. The heterogeneity in the healthy human immune system, and the immunological changes that portend various diseases, have been only partially described. Their comprehensive elucidation has been termed the 'Human Immunology Project'. The accurate measurement of variations in the human immune system requires precise and standardized assays to distinguish true biological changes from technical artefacts. Thus, to be successful, the Human Immunology Project will require standardized assays for immunophenotyping humans in health and disease. A major tool in this effort is flow cytometry, which remains highly variable with regard to sample handling, reagents, instrument setup and data analysis. In this Review, we outline the current state of standardization of flow cytometry assays and summarize the steps that are required to enable the Human Immunology Project.