Comprehensive immunophenotyping of whole blood by multi-parameter flow cytometry for use in clinical trial immune monitoring

Immune monitoring by flow cytometry is a fast and highly informative way to assess changes in immunophenotypes longitudinally to study disease progression and the effects of immunotherapies. Utilising a total of less than 1 mL of peripheral blood, we developed a robust immune monitoring method to comprehensively immunophenotype unmanipulated whole blood using five 9- to 14-colour flow cytometric panels to monitor absolute cell number and frequencies of T cell, B cell, dendritic cell, natural killer cell and granulocyte subsets as well as activation and proliferation of some of these cell populations.

Precision and variability of intra- and inter-operator staining were assessed, showing a CV of less than 20% between triplicate stains and between stains from different operators, even for cell populations with frequencies down to 0.1% and an acquired event of 10 cells, suggesting that this method is very robust with high precision. This acceptance criterion of a CV of 20% is used when training both internal and external scientists. In addition, we demonstrated that staining must be performed within six hours of sample collection to prevent any major changes of phenotypes due to the age of specimen, however, some T cell phenotypes are stable up to 48 hours post collection.

We now routinely use whole blood flow cytometry for immune monitoring individuals with Type 1 Diabetes (T1D) and those enrolled in various clinical trials and are currently standardising this method across multiple international laboratories as part of INNODIA, enabling fair and direct comparisons between different study sites. Same flow panels have been used to investigate phenotypic differences between peripheral blood and lymph node samples both from healthy controls and T1D individuals. We propose that these panels can be adopted for monitoring individuals not only participating in T1D studies but also for other immune-related diseases.