B cell-derived GABA elicits IL-10+ macrophages to limit anti-tumour immunity

Small, soluble metabolites not only are essential intermediates in intracellular biochemical processes, but can also influence neighbouring cells when released into the extracellular milieu(1-3). Here we identify the metabolite and neurotransmitter GABA as a candidate signalling molecule synthesized and secreted by activated B cells and plasma cells. We show that B cell-derived GABA promotes monocyte differentiation into anti-inflammatory macrophages that secrete interleukin-10 and inhibit CD8(+) T cell killer function. In mice, B cell deficiency or B cell-specific inactivation of the GABA-generating enzyme GAD67 enhances anti-tumour responses. Our study reveals that, in addition to cytokines and membrane proteins, small metabolites derived from B-lineage cells have immunoregulatory functions, which may be pharmaceutical targets allowing fine-tuning of immune responses.

Automated summary

This study reveals that small metabolites like GABA derived from B-lineage cells can influence immune responses by promoting anti-inflammatory macrophages and enhancing anti-tumour responses. The findings suggest that targeting these metabolites may offer a new approach to immunoregulation.