Abstract Text: Among key antibody-independent B-cell functions is their capacity for context-dependent secretion of distinct cytokine profiles that shapes immune responses relevant in both health and disease, such as the CNS inflammatory condition multiple sclerosis (MS). Here we investigated fundamental mechanisms underlying regulation of the balance between human B-cell pro- and anti-inflammatory cytokine responses and their impact on CNS inflammation. Compared to anti-inflammatory cytokine producing B cells (IL-10+ B cells), the generation of pro-inflammatory cytokine-expressing B cells requires higher metabolic activity and limiting mitochondrial-respiration (but not glycolysis) mediates an anti-inflammatory B-cell cytokine shift, and dampens the ability of B cells to promote myeloid cell responses. Upon stimulation, B cells from MS patients exhibit higher mitochondrial respiration and inhibition of their mitochondrial respiration restores the balance of B-cell cytokines. Limiting B-cell mitochondrial respiration specifically in B cells decreases pro-inflammatory immune responses and diminishes clinical disease severity in EAE, a commonly used murine model of neuroinflammation. Mechanistic studies further reveal that mitochondrial derived ATP is involved in shaping B-cell cytokine responses through the purinergic receptor P2RX7. Blockade of P2RX7 reduces B-cell proinflammatory cytokine production both in vitro and in vivo, and ameliorates clinical severity of EAE in vivo. Together, our study reveals a fundamental mechanism involving metabolic regulation of B-cell pro- and anti-inflammatory cytokine responses; identifies ATP and its metabolites as a ‘fourth signal’ shaping B-cell responses; and indicates that non-depleting therapeutic strategies may restore a normal B-cell cytokine balance in human autoimmune disease by targeting B-cell metabolism.
