# Expression of TIM-3 and Gal-9 Immune Checkpoints in Chronic Lymphocytic Leukemia: The Potential Role of Interleukin-27

## TL;DR

This study shows that IL-27 increases TIM-3 and Gal-9 immune checkpoints in CLL, which may worsen T cell exhaustion and disease progression.

## Contribution

The study is the first to show IL-27's effect on TIM-3 and Gal-9 expression in chronic lymphocytic leukemia cells.

## Key findings

- IL-27 increased TIM-3 on CD8+ T cells, indicating T cell exhaustion.
- IL-27 modestly increased Gal-9 in lymphocytes and reduced CD4+ T cells.
- Changes suggest IL-27 may contribute to immunosuppression in CLL.

## Abstract

Background: Chronic lymphocytic leukemia (CLL) is characterized by malignant B lymphocyte accumulation and progressive immune dysfunction. The immune checkpoint molecule TIM-3 and its ligand galectin-9 (Gal-9) contribute to T cell exhaustion, impairing anti-tumour immunity. Interleukin-27 (IL-27) has pleiotropic immunomodulatory properties, but its impact on TIM-3 and Gal-9 expression in CLL remains unclear. Methods: Peripheral blood mononuclear cells (PBMCs) from 20 treatment-naive CLL patients were cultured with or without IL-27 (100 ng/mL) for 72 h. Flow cytometry assessed TIM-3 and Gal-9 expression on CD4+, CD8+, and CD19+ cells. Results: IL-27 stimulation significantly increased TIM-3 expression on CD8+ T cells (2.18 ± 0.32% vs. 3.09 ± 0.49%, p = 0.009), a hallmark of T cell exhaustion. IL-27 also modestly increased intracellular Gal-9 levels in total lymphocytes (93.91 ± 1.17% vs. 96.55 ± 0.67%, p = 0.005). Additionally, IL-27 reduced CD4+ T cell proportions (26.71 ± 4.19% vs. 22.01 ± 3.23%, p = 0.010). Although numerically modest, these changes may be biologically pertinent in the context of checkpoint-mediated CD8+ T-cell exhaustion. Conclusions: IL-27 may enhance immunosuppressive mechanisms in CLL by modulating immune checkpoint expression, potentially contributing to disease progression. These ex vivo findings in PBMCs from CLL patients indicate the IL-27-associated modulation of checkpoint expression under the conditions tested. In the absence of parallel healthy-donor controls, CLL specificity cannot be established in this study.