Immune Checkpoint Analysis of T Effectors and Regulatory T Cells in Patients with CML Reveals Increased Expression at Diagnosis and with Refractory Disease

• Published in: Blood 2021-11, Vol.138 (Supplement 1), p.2545-2545
• Main Authors: Harrington, Patrick, Dillon, Richard, Radia, Deepti H., McLornan, Donal P., Woodley, Claire, Asirvatham, Susan, Raj, Kavita, Curto-Garcia, Natalia, Kordasti, Shahram, Harrison, Claire N., de Lavallade, Hugues
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2021-150533

Introduction: The search for potential new targets to improve outcomes in patients with CML is ongoing, with a view to improve treatment efficacy for those with refractory disease and increase the proportion of those eligible to attempt TKI discontinuation. CML is recognised as a particularly immune sensitive tumour and as such immune checkpoint inhibitors, which can enhance inherent immune surveillance mechanisms are an attractive proposition. Methods: We performed flow cytometric analysis of peripheral blood mononuclear cells for expression of PD1, CTLA-4, TIM-3 and LAG-3 on T effectors and regulatory T cells. T effectors included CD4+ and CD8+ subsets and a gating strategy of CD4+/CD25+/CD127 lo/FOXP3+ cells for Tregs was employed, whilst FOXP3 hi/CD45RA-ve cells denoted effector Tregs. FMO controls were used to determine positive populations for each immune checkpoint molecule under investigation. Results: Samples from 22 patients were analysed, including samples from two different time points in 4 patients. This included patients at diagnosis (n=8), those with refractory disease defined as