IL3-Driven T Cell-Basophil Crosstalk Enhances Antitumor Immunity

Area of Science:

• Immunology
• Cancer Biology
• T cell biology

Background:

• Cytotoxic T lymphocytes (CTLs) are crucial for anti-cancer immunity but are often impaired by the tumor microenvironment, leading to exhaustion.
• Interleukin-3 (IL3) dysregulation is implicated in compromised CTL function within tumors.

Purpose of the Study:

• To investigate the role of IL3 in modulating CTLs and orchestrating anti-tumor immunity.
• To explore the therapeutic potential of IL3 supplementation in enhancing anti-cancer responses.

Main Methods:

• Assessed IL3 production in intratumoral CTLs and correlated it with cytotoxic function.
• Administered recombinant IL3, IL3-expressing tumor cells, or IL3-engineered CD8+ T cells to augment IL3 levels.
• Utilized Rag1 knockout mice and CD8+ T-cell depletion models to confirm CTL dependence.
• Investigated the role of basophils and IL4 in mediating IL3's effects.
• Examined IL4 production by basophils and its impact on CTLs in IL4 knockout mice.

Main Results:

• Intratumoral CTLs showed decreased IL3 production correlating with reduced cytotoxic activity.
• IL3 supplementation enhanced CTL activity and conferred protection against tumor progression.
• The therapeutic effect of IL3 was dependent on CTLs and involved IL3-mediated cross-talk with basophils.
• IL3-activated basophils produced IL4, which boosted CTL IFNγ production and viability, crucial for anti-tumor immunity.

Conclusions:

• IL3 plays a critical role in maintaining CTL function and orchestrating anti-tumor immunity through a CTL-basophil-IL4 axis.
• Augmenting IL3 levels represents a promising strategy for enhancing cancer immunotherapy efficacy.