B cells secrete GABA, which provokes a pro-tumor immune microenvironment

Area of Science:

• Immunology
• Metabolomics
• Cancer Biology

Background:

• B cells play diverse roles in immunity, including immune regulation.
• Tumor microenvironments often exhibit immunosuppressive characteristics.
• Metabolite production by immune cells can influence immune responses.

Purpose of the Study:

• To investigate the impact of foreign antigen stimulation on lymphatic metabolite production.
• To elucidate the role of B cell-secreted metabolites in immune regulation.
• To understand the contribution of these mechanisms to tumor progression.

Main Methods:

• Analysis of lymphatic metabolite profiles following antigen stimulation.
• Characterization of B cell-secreted metabolites, specifically gamma-aminobutyric acid (GABA).
• In vitro and in vivo studies assessing the effects of GABA on macrophage and T cell function.

Main Results:

• Foreign antigen stimulation induced significant alterations in lymphatic metabolite production.
• B cells were identified as a source of secreted GABA within the lymphatic system.
• GABA reprogrammed macrophages towards an immunosuppressive phenotype and reduced T cell cytotoxicity.
• This B cell-mediated immune suppression was linked to facilitating tumor progression.

Conclusions:

• B cells regulate immune suppression through the secretion of GABA, a key lymphatic metabolite.
• GABA reprograms macrophages and inhibits T cell-mediated anti-tumor immunity.
• This newly identified mechanism highlights a role for B cells in promoting tumor progression via metabolic reprogramming.